diff --git a/ClosedXML/Excel/XLWorkbook.cs b/ClosedXML/Excel/XLWorkbook.cs
index 1177678..3f72e5c 100644
--- a/ClosedXML/Excel/XLWorkbook.cs
+++ b/ClosedXML/Excel/XLWorkbook.cs
@@ -401,14 +401,7 @@
 
         public Boolean TryGetWorksheet(String name, out IXLWorksheet worksheet)
         {
-            if (Worksheets.Any(w => string.Equals(w.Name, XLWorksheets.TrimSheetName(name), StringComparison.OrdinalIgnoreCase)))
-            {
-                worksheet = Worksheet(name);
-                return true;
-            }
-
-            worksheet = null;
-            return false;
+            return Worksheets.TryGetWorksheet(name, out worksheet);
         }
 
         public IXLRange RangeFromFullAddress(String rangeAddress, out IXLWorksheet ws)
diff --git a/ClosedXML/Excel/XLWorksheets.cs b/ClosedXML/Excel/XLWorksheets.cs
index 9061e1d..af69de6 100644
--- a/ClosedXML/Excel/XLWorksheets.cs
+++ b/ClosedXML/Excel/XLWorksheets.cs
@@ -47,7 +47,7 @@
         public bool TryGetWorksheet(string sheetName, out IXLWorksheet worksheet)
         {
             XLWorksheet w;
-            if (_worksheets.TryGetValue(sheetName, out w))
+            if (_worksheets.TryGetValue(TrimSheetName(sheetName).ToLowerInvariant(), out w))
             {
                 worksheet = w;
                 return true;
@@ -70,7 +70,7 @@
 
             XLWorksheet w;
 
-            if (_worksheets.TryGetValue(sheetName, out w))
+            if (_worksheets.TryGetValue(sheetName.ToLowerInvariant(), out w))
                 return w;
 
             var wss = _worksheets.Where(ws => string.Equals(ws.Key, sheetName, StringComparison.OrdinalIgnoreCase));
@@ -118,12 +118,12 @@
             if (_worksheets.Any(ws => ws.Key.Equals(sheetName, StringComparison.OrdinalIgnoreCase)))
                 throw new ArgumentException(String.Format("A worksheet with the same name ({0}) has already been added.", sheetName), nameof(sheetName));
 
-            _worksheets.Add(sheetName, sheet);
+            _worksheets.Add(sheetName.ToLowerInvariant(), sheet);
         }
 
         public void Delete(String sheetName)
         {
-            Delete(_worksheets[sheetName].Position);
+            Delete(_worksheets[sheetName.ToLowerInvariant()].Position);
         }
 
         public void Delete(Int32 position)
@@ -178,14 +178,14 @@
 
         public void Rename(String oldSheetName, String newSheetName)
         {
-            if (String.IsNullOrWhiteSpace(oldSheetName) || !_worksheets.ContainsKey(oldSheetName)) return;
+            if (String.IsNullOrWhiteSpace(oldSheetName) || !_worksheets.ContainsKey(oldSheetName.ToLowerInvariant())) return;
 
             if (!oldSheetName.Equals(newSheetName, StringComparison.OrdinalIgnoreCase)
                 && _worksheets.Any(ws1 => ws1.Key.Equals(newSheetName, StringComparison.OrdinalIgnoreCase)))
                 throw new ArgumentException(String.Format("A worksheet with the same name ({0}) has already been added.", newSheetName), nameof(newSheetName));
 
-            var ws = _worksheets[oldSheetName];
-            _worksheets.Remove(oldSheetName);
+            var ws = _worksheets[oldSheetName.ToLowerInvariant()];
+            _worksheets.Remove(oldSheetName.ToLowerInvariant());
             Add(newSheetName, ws);
         }
     }
diff --git a/ClosedXML_Tests/Excel/Worksheets/XLWorksheetTests.cs b/ClosedXML_Tests/Excel/Worksheets/XLWorksheetTests.cs
index 76f612e..33fafed 100644
--- a/ClosedXML_Tests/Excel/Worksheets/XLWorksheetTests.cs
+++ b/ClosedXML_Tests/Excel/Worksheets/XLWorksheetTests.cs
@@ -161,6 +161,27 @@
         }
 
         [Test]
+        public void TryGetWorksheet()
+        {
+            using (var wb = new XLWorkbook())
+            {
+                var ws1 = wb.AddWorksheet("Sheet1");
+                var ws2 = wb.AddWorksheet("Sheet2");
+
+                IXLWorksheet ws;
+                Assert.IsTrue(wb.Worksheets.TryGetWorksheet("Sheet1", out ws));
+                Assert.IsTrue(wb.Worksheets.TryGetWorksheet("sheet1", out ws));
+                Assert.IsTrue(wb.Worksheets.TryGetWorksheet("sHEeT1", out ws));
+                Assert.IsFalse(wb.Worksheets.TryGetWorksheet("Sheeeet2", out ws));
+
+                Assert.IsTrue(wb.TryGetWorksheet("Sheet1", out ws));
+                Assert.IsTrue(wb.TryGetWorksheet("sheet1", out ws));
+                Assert.IsTrue(wb.TryGetWorksheet("sHEeT1", out ws));
+                Assert.IsFalse(wb.TryGetWorksheet("Sheeeet2", out ws));
+            }
+        }
+
+        [Test]
         public void HideWorksheet()
         {
             using (var ms = new MemoryStream())