diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3cd3e9a1..f37d67bc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+## [Unreleased]
+
+### Fixed
+
+- Sheet title can contain exclamation mark - [#325](https://github.com/PHPOffice/PhpSpreadsheet/issues/325)
+
 ## [1.4.1] - 2018-09-30
 
 ### Fixed
diff --git a/src/PhpSpreadsheet/Calculation/Calculation.php b/src/PhpSpreadsheet/Calculation/Calculation.php
index 79b98b95..5dc74ef0 100644
--- a/src/PhpSpreadsheet/Calculation/Calculation.php
+++ b/src/PhpSpreadsheet/Calculation/Calculation.php
@@ -3478,19 +3478,15 @@ class Calculation
                     $testPrevOp = $stack->last(1);
                     if ($testPrevOp['value'] == ':') {
                         $startRowColRef = $output[count($output) - 1]['value'];
-                        $rangeWS1 = '';
-                        if (strpos('!', $startRowColRef) !== false) {
-                            list($rangeWS1, $startRowColRef) = explode('!', $startRowColRef);
-                        }
+                        list($rangeWS1, $startRowColRef) = Worksheet::extractSheetTitle($startRowColRef, true);
                         if ($rangeWS1 != '') {
                             $rangeWS1 .= '!';
                         }
-                        $rangeWS2 = $rangeWS1;
-                        if (strpos('!', $val) !== false) {
-                            list($rangeWS2, $val) = explode('!', $val);
-                        }
+                        list($rangeWS2, $val) = Worksheet::extractSheetTitle($val, true);
                         if ($rangeWS2 != '') {
                             $rangeWS2 .= '!';
+                        } else {
+                            $rangeWS2 = $rangeWS1;
                         }
                         if ((is_int($startRowColRef)) && (ctype_digit($val)) &&
                             ($startRowColRef <= 1048576) && ($val <= 1048576)) {
@@ -3665,13 +3661,12 @@ class Calculation
                     case ':':            //    Range
                         $sheet1 = $sheet2 = '';
                         if (strpos($operand1Data['reference'], '!') !== false) {
-                            list($sheet1, $operand1Data['reference']) = explode('!', $operand1Data['reference']);
+                            list($sheet1, $operand1Data['reference']) = Worksheet::extractSheetTitle($operand1Data['reference'], true);
                         } else {
                             $sheet1 = ($pCellParent !== null) ? $pCellWorksheet->getTitle() : '';
                         }
-                        if (strpos($operand2Data['reference'], '!') !== false) {
-                            list($sheet2, $operand2Data['reference']) = explode('!', $operand2Data['reference']);
-                        } else {
+                        list($sheet2, $operand2Data['reference']) = Worksheet::extractSheetTitle($operand2Data['reference'], true);
+                        if (empty($sheet2)) {
                             $sheet2 = $sheet1;
                         }
                         if ($sheet1 == $sheet2) {
diff --git a/src/PhpSpreadsheet/Calculation/LookupRef.php b/src/PhpSpreadsheet/Calculation/LookupRef.php
index 71550a7b..8bd778d9 100644
--- a/src/PhpSpreadsheet/Calculation/LookupRef.php
+++ b/src/PhpSpreadsheet/Calculation/LookupRef.php
@@ -4,6 +4,7 @@ namespace PhpOffice\PhpSpreadsheet\Calculation;
 
 use PhpOffice\PhpSpreadsheet\Cell\Cell;
 use PhpOffice\PhpSpreadsheet\Cell\Coordinate;
+use PhpOffice\PhpSpreadsheet\Worksheet\Worksheet;
 
 class LookupRef
 {
@@ -96,9 +97,7 @@ class LookupRef
                 return (int) Coordinate::columnIndexFromString($columnKey);
             }
         } else {
-            if (strpos($cellAddress, '!') !== false) {
-                list($sheet, $cellAddress) = explode('!', $cellAddress);
-            }
+            list($sheet, $cellAddress) = Worksheet::extractSheetTitle($cellAddress, true);
             if (strpos($cellAddress, ':') !== false) {
                 list($startAddress, $endAddress) = explode(':', $cellAddress);
                 $startAddress = preg_replace('/[^a-z]/i', '', $startAddress);
@@ -175,9 +174,7 @@ class LookupRef
                 }
             }
         } else {
-            if (strpos($cellAddress, '!') !== false) {
-                list($sheet, $cellAddress) = explode('!', $cellAddress);
-            }
+            list($sheet, $cellAddress) = Worksheet::extractSheetTitle($cellAddress, true);
             if (strpos($cellAddress, ':') !== false) {
                 list($startAddress, $endAddress) = explode(':', $cellAddress);
                 $startAddress = preg_replace('/\D/', '', $startAddress);
@@ -297,7 +294,7 @@ class LookupRef
             }
 
             if (strpos($cellAddress, '!') !== false) {
-                list($sheetName, $cellAddress) = explode('!', $cellAddress);
+                list($sheetName, $cellAddress) = Worksheet::extractSheetTitle($cellAddress, true);
                 $sheetName = trim($sheetName, "'");
                 $pSheet = $pCell->getWorksheet()->getParent()->getSheetByName($sheetName);
             } else {
@@ -308,7 +305,7 @@ class LookupRef
         }
 
         if (strpos($cellAddress, '!') !== false) {
-            list($sheetName, $cellAddress) = explode('!', $cellAddress);
+            list($sheetName, $cellAddress) = Worksheet::extractSheetTitle($cellAddress, true);
             $sheetName = trim($sheetName, "'");
             $pSheet = $pCell->getWorksheet()->getParent()->getSheetByName($sheetName);
         } else {
@@ -361,7 +358,7 @@ class LookupRef
 
         $sheetName = null;
         if (strpos($cellAddress, '!')) {
-            list($sheetName, $cellAddress) = explode('!', $cellAddress);
+            list($sheetName, $cellAddress) = Worksheet::extractSheetTitle($cellAddress, true);
             $sheetName = trim($sheetName, "'");
         }
         if (strpos($cellAddress, ':')) {
diff --git a/src/PhpSpreadsheet/Cell/Coordinate.php b/src/PhpSpreadsheet/Cell/Coordinate.php
index 366ec492..1bca6f44 100644
--- a/src/PhpSpreadsheet/Cell/Coordinate.php
+++ b/src/PhpSpreadsheet/Cell/Coordinate.php
@@ -3,6 +3,7 @@
 namespace PhpOffice\PhpSpreadsheet\Cell;
 
 use PhpOffice\PhpSpreadsheet\Exception;
+use PhpOffice\PhpSpreadsheet\Worksheet\Worksheet;
 
 /**
  * Helper class to manipulate cell coordinates.
@@ -70,11 +71,7 @@ abstract class Coordinate
         }
 
         // Split out any worksheet name from the reference
-        $worksheet = '';
-        $cellAddress = explode('!', $pCoordinateString);
-        if (count($cellAddress) > 1) {
-            list($worksheet, $pCoordinateString) = $cellAddress;
-        }
+        list($worksheet, $pCoordinateString) = Worksheet::extractSheetTitle($pCoordinateString, true);
         if ($worksheet > '') {
             $worksheet .= '!';
         }
@@ -105,11 +102,7 @@ abstract class Coordinate
         }
 
         // Split out any worksheet name from the coordinate
-        $worksheet = '';
-        $cellAddress = explode('!', $pCoordinateString);
-        if (count($cellAddress) > 1) {
-            list($worksheet, $pCoordinateString) = $cellAddress;
-        }
+        list($worksheet, $pCoordinateString) = Worksheet::extractSheetTitle($pCoordinateString, true);
         if ($worksheet > '') {
             $worksheet .= '!';
         }
diff --git a/src/PhpSpreadsheet/Chart/DataSeriesValues.php b/src/PhpSpreadsheet/Chart/DataSeriesValues.php
index a726219c..fda6ccdf 100644
--- a/src/PhpSpreadsheet/Chart/DataSeriesValues.php
+++ b/src/PhpSpreadsheet/Chart/DataSeriesValues.php
@@ -354,11 +354,7 @@ class DataSeriesValues
                 }
                 unset($dataValue);
             } else {
-                $cellRange = explode('!', $this->dataSource);
-                if (count($cellRange) > 1) {
-                    list(, $cellRange) = $cellRange;
-                }
-
+                list($worksheet, $cellRange) = Worksheet::extractSheetTitle($this->dataSource, true);
                 $dimensions = Coordinate::rangeDimension(str_replace('$', '', $cellRange));
                 if (($dimensions[0] == 1) || ($dimensions[1] == 1)) {
                     $this->dataValues = Functions::flattenArray($newDataValues);
diff --git a/src/PhpSpreadsheet/Reader/Gnumeric.php b/src/PhpSpreadsheet/Reader/Gnumeric.php
index af2ed8e4..dd92f153 100644
--- a/src/PhpSpreadsheet/Reader/Gnumeric.php
+++ b/src/PhpSpreadsheet/Reader/Gnumeric.php
@@ -16,6 +16,7 @@ use PhpOffice\PhpSpreadsheet\Style\Border;
 use PhpOffice\PhpSpreadsheet\Style\Borders;
 use PhpOffice\PhpSpreadsheet\Style\Fill;
 use PhpOffice\PhpSpreadsheet\Style\Font;
+use PhpOffice\PhpSpreadsheet\Worksheet\Worksheet;
 use XMLReader;
 
 class Gnumeric extends BaseReader
@@ -784,7 +785,7 @@ class Gnumeric extends BaseReader
                     continue;
                 }
 
-                $range = explode('!', $range);
+                $range = Worksheet::extractSheetTitle($range, true);
                 $range[0] = trim($range[0], "'");
                 if ($worksheet = $spreadsheet->getSheetByName($range[0])) {
                     $extractedRange = str_replace('$', '', $range[1]);
diff --git a/src/PhpSpreadsheet/Reader/Xls.php b/src/PhpSpreadsheet/Reader/Xls.php
index e6803c78..d08d85e8 100644
--- a/src/PhpSpreadsheet/Reader/Xls.php
+++ b/src/PhpSpreadsheet/Reader/Xls.php
@@ -1213,7 +1213,7 @@ class Xls extends BaseReader
                             // $range should look like one of these
                             //        Foo!$C$7:$J$66
                             //        Bar!$A$1:$IV$2
-                            $explodes = explode('!', $range); // FIXME: what if sheetname contains exclamation mark?
+                            $explodes = Worksheet::extractSheetTitle($range, true);
                             $sheetName = trim($explodes[0], "'");
                             if (count($explodes) == 2) {
                                 if (strpos($explodes[1], ':') === false) {
@@ -1243,8 +1243,8 @@ class Xls extends BaseReader
                             // $range should look like this one of these
                             //        Sheet!$A$1:$B$65536
                             //        Sheet!$A$1:$IV$2
-                            $explodes = explode('!', $range);
-                            if (count($explodes) == 2) {
+                            if (strpos($range, '!') !== false) {
+                                $explodes = Worksheet::extractSheetTitle($range, true);
                                 if ($docSheet = $this->spreadsheet->getSheetByName($explodes[0])) {
                                     $extractedRange = $explodes[1];
                                     $extractedRange = str_replace('$', '', $extractedRange);
@@ -1270,9 +1270,8 @@ class Xls extends BaseReader
                 }
             } else {
                 // Extract range
-                $explodes = explode('!', $definedName['formula']);
-
-                if (count($explodes) == 2) {
+                if (strpos($definedName['formula'], '!') !== false) {
+                    $explodes = Worksheet::extractSheetTitle($definedName['formula'], true);
                     if (($docSheet = $this->spreadsheet->getSheetByName($explodes[0])) ||
                         ($docSheet = $this->spreadsheet->getSheetByName(trim($explodes[0], "'")))) {
                         $extractedRange = $explodes[1];
diff --git a/src/PhpSpreadsheet/Reader/Xlsx.php b/src/PhpSpreadsheet/Reader/Xlsx.php
index a7709852..dfb4b825 100644
--- a/src/PhpSpreadsheet/Reader/Xlsx.php
+++ b/src/PhpSpreadsheet/Reader/Xlsx.php
@@ -1833,8 +1833,7 @@ class Xlsx extends BaseReader
                                                 $rangeSets = preg_split("/'(.*?)'(?:![A-Z0-9]+:[A-Z0-9]+,?)/", $extractedRange, PREG_SPLIT_NO_EMPTY);
                                                 $newRangeSets = [];
                                                 foreach ($rangeSets as $rangeSet) {
-                                                    $range = explode('!', $rangeSet); // FIXME: what if sheetname contains exclamation mark?
-                                                    $rangeSet = isset($range[1]) ? $range[1] : $range[0];
+                                                    list($sheetName, $rangeSet) = Worksheet::extractSheetTitle($rangeSet, true);
                                                     if (strpos($rangeSet, ':') === false) {
                                                         $rangeSet = $rangeSet . ':' . $rangeSet;
                                                     }
@@ -1881,8 +1880,8 @@ class Xlsx extends BaseReader
                                             break;
                                         default:
                                             if ($mapSheetId[(int) $definedName['localSheetId']] !== null) {
-                                                $range = explode('!', (string) $definedName);
-                                                if (count($range) == 2) {
+                                                if (strpos((string) $definedName, '!') !== false) {
+                                                    $range = Worksheet::extractSheetTitle((string) $definedName, true);
                                                     $range[0] = str_replace("''", "'", $range[0]);
                                                     $range[0] = str_replace("'", '', $range[0]);
                                                     if ($worksheet = $docSheet->getParent()->getSheetByName($range[0])) {
@@ -1908,8 +1907,7 @@ class Xlsx extends BaseReader
                                         $locatedSheet = $excel->getSheetByName($extractedSheetName);
 
                                         // Modify range
-                                        $range = explode('!', $extractedRange);
-                                        $extractedRange = isset($range[1]) ? $range[1] : $range[0];
+                                        list($worksheetName, $extractedRange) = Worksheet::extractSheetTitle($extractedRange, true);
                                     }
 
                                     if ($locatedSheet !== null) {
diff --git a/src/PhpSpreadsheet/Worksheet/AutoFilter.php b/src/PhpSpreadsheet/Worksheet/AutoFilter.php
index b92c986e..333aa1b8 100644
--- a/src/PhpSpreadsheet/Worksheet/AutoFilter.php
+++ b/src/PhpSpreadsheet/Worksheet/AutoFilter.php
@@ -89,11 +89,8 @@ class AutoFilter
      */
     public function setRange($pRange)
     {
-        // Uppercase coordinate
-        $cellAddress = explode('!', strtoupper($pRange));
-        if (count($cellAddress) > 1) {
-            list($worksheet, $pRange) = $cellAddress;
-        }
+        // extract coordinate
+        list($worksheet, $pRange) = Worksheet::extractSheetTitle($pRange, true);
 
         if (strpos($pRange, ':') !== false) {
             $this->range = $pRange;
diff --git a/src/PhpSpreadsheet/Worksheet/Worksheet.php b/src/PhpSpreadsheet/Worksheet/Worksheet.php
index 42dcd69b..f4ee4b60 100644
--- a/src/PhpSpreadsheet/Worksheet/Worksheet.php
+++ b/src/PhpSpreadsheet/Worksheet/Worksheet.php
@@ -2729,12 +2729,12 @@ class Worksheet implements IComparable
     public static function extractSheetTitle($pRange, $returnRange = false)
     {
         // Sheet title included?
-        if (($sep = strpos($pRange, '!')) === false) {
-            return '';
+        if (($sep = strrpos($pRange, '!')) === false) {
+            return $returnRange ? ['', $pRange] : '';
         }
 
         if ($returnRange) {
-            return [trim(substr($pRange, 0, $sep), "'"), substr($pRange, $sep + 1)];
+            return [substr($pRange, 0, $sep), substr($pRange, $sep + 1)];
         }
 
         return substr($pRange, $sep + 1);
diff --git a/src/PhpSpreadsheet/Writer/Xls/Parser.php b/src/PhpSpreadsheet/Writer/Xls/Parser.php
index 00ead3c2..e87d09a2 100644
--- a/src/PhpSpreadsheet/Writer/Xls/Parser.php
+++ b/src/PhpSpreadsheet/Writer/Xls/Parser.php
@@ -3,6 +3,7 @@
 namespace PhpOffice\PhpSpreadsheet\Writer\Xls;
 
 use PhpOffice\PhpSpreadsheet\Shared\StringHelper;
+use PhpOffice\PhpSpreadsheet\Worksheet\Worksheet as PhpspreadsheetWorksheet;
 use PhpOffice\PhpSpreadsheet\Writer\Exception as WriterException;
 
 // Original file header of PEAR::Spreadsheet_Excel_Writer_Parser (used as the base for this class):
@@ -643,7 +644,7 @@ class Parser
     private function convertRange3d($token)
     {
         // Split the ref at the ! symbol
-        list($ext_ref, $range) = explode('!', $token);
+        list($ext_ref, $range) = PhpspreadsheetWorksheet::extractSheetTitle($token, true);
 
         // Convert the external reference part (different for BIFF8)
         $ext_ref = $this->getRefIndex($ext_ref);
@@ -695,7 +696,7 @@ class Parser
     private function convertRef3d($cell)
     {
         // Split the ref at the ! symbol
-        list($ext_ref, $cell) = explode('!', $cell);
+        list($ext_ref, $cell) = PhpspreadsheetWorksheet::extractSheetTitle($cell, true);
 
         // Convert the external reference part (different for BIFF8)
         $ext_ref = $this->getRefIndex($ext_ref);
diff --git a/src/PhpSpreadsheet/Writer/Xlsx/Workbook.php b/src/PhpSpreadsheet/Writer/Xlsx/Workbook.php
index 43a1916f..e3ddb03c 100644
--- a/src/PhpSpreadsheet/Writer/Xlsx/Workbook.php
+++ b/src/PhpSpreadsheet/Writer/Xlsx/Workbook.php
@@ -339,9 +339,7 @@ class Workbook extends WriterPart
             $range = Coordinate::splitRange($autoFilterRange);
             $range = $range[0];
             //    Strip any worksheet ref so we can make the cell ref absolute
-            if (strpos($range[0], '!') !== false) {
-                list($ws, $range[0]) = explode('!', $range[0]);
-            }
+            list($ws, $range[0]) = Worksheet::extractSheetTitle($range[0], true);
 
             $range[0] = Coordinate::absoluteCoordinate($range[0]);
             $range[1] = Coordinate::absoluteCoordinate($range[1]);
diff --git a/src/PhpSpreadsheet/Writer/Xlsx/Worksheet.php b/src/PhpSpreadsheet/Writer/Xlsx/Worksheet.php
index cb46a121..78a62e9e 100644
--- a/src/PhpSpreadsheet/Writer/Xlsx/Worksheet.php
+++ b/src/PhpSpreadsheet/Writer/Xlsx/Worksheet.php
@@ -748,9 +748,7 @@ class Worksheet extends WriterPart
             $range = Coordinate::splitRange($autoFilterRange);
             $range = $range[0];
             //    Strip any worksheet ref
-            if (strpos($range[0], '!') !== false) {
-                list($ws, $range[0]) = explode('!', $range[0]);
-            }
+            list($ws, $range[0]) = PhpspreadsheetWorksheet::extractSheetTitle($range[0], true);
             $range = implode(':', $range);
 
             $objWriter->writeAttribute('ref', str_replace('$', '', $range));
diff --git a/tests/PhpSpreadsheetTests/Worksheet/WorksheetTest.php b/tests/PhpSpreadsheetTests/Worksheet/WorksheetTest.php
index 5dfa8259..46df9405 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/WorksheetTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/WorksheetTest.php
@@ -130,4 +130,30 @@ class WorksheetTest extends TestCase
         $worksheet->freezePane('B2');
         self::assertSame('B2', $worksheet->getTopLeftCell());
     }
+
+    public function extractSheetTitleProvider()
+    {
+        return [
+            ['B2', '', '', 'B2'],
+            ['testTitle!B2', 'testTitle', 'B2', 'B2'],
+            ['test!Title!B2', 'test!Title', 'B2', 'B2'],
+        ];
+    }
+
+    /**
+     * @param string $range
+     * @param string $expectTitle
+     * @param string $expectCell
+     * @param string $expectCell2
+     * @dataProvider extractSheetTitleProvider
+     */
+    public function testExtractSheetTitle($range, $expectTitle, $expectCell, $expectCell2)
+    {
+        // only cell reference
+        self::assertSame($expectCell, Worksheet::extractSheetTitle($range));
+        // with title in array
+        $arRange = Worksheet::extractSheetTitle($range, true);
+        self::assertSame($expectTitle, $arRange[0]);
+        self::assertSame($expectCell2, $arRange[1]);
+    }
 }
diff --git a/tests/data/CellAbsoluteCoordinate.php b/tests/data/CellAbsoluteCoordinate.php
index d5eefca1..86487585 100644
--- a/tests/data/CellAbsoluteCoordinate.php
+++ b/tests/data/CellAbsoluteCoordinate.php
@@ -42,11 +42,11 @@ return [
         '\'Worksheet1\'!$AI256',
     ],
     [
-        '\'Worksheet1\'!$AI$256',
-        '\'Worksheet1\'!AI$256',
+        '\'Work!sheet1!\'!$AI$256',
+        '\'Work!sheet1!\'!AI$256',
     ],
     [
-        '\'Worksheet1\'!$AI$256',
-        '\'Worksheet1\'!$AI$256',
+        '\'Work!sheet1!\'!$AI$256',
+        '\'Work!sheet1!\'!$AI$256',
     ],
 ];
diff --git a/tests/data/CellAbsoluteReference.php b/tests/data/CellAbsoluteReference.php
index ccf4f33f..71dac545 100644
--- a/tests/data/CellAbsoluteReference.php
+++ b/tests/data/CellAbsoluteReference.php
@@ -26,12 +26,12 @@ return [
         'AI2012',
     ],
     [
-        '\'Worksheet1\'!$AI$256',
-        '\'Worksheet1\'!AI256',
+        '\'Work!sheet1\'!$AI$256',
+        '\'Work!sheet1\'!AI256',
     ],
     [
-        'Worksheet1!$AI$256',
-        'Worksheet1!AI256',
+        'Work!sheet1!$AI$256',
+        'Work!sheet1!AI256',
     ],
     [
         '\'Data Worksheet\'!$AI$256',