diff --git a/src/Runner.Sdk/Util/IOUtil.cs b/src/Runner.Sdk/Util/IOUtil.cs
index da4a8a09bcf..e0b5b3394f7 100644
--- a/src/Runner.Sdk/Util/IOUtil.cs
+++ b/src/Runner.Sdk/Util/IOUtil.cs
@@ -459,6 +459,34 @@ public static void CreateEmptyFile(string path)
             File.WriteAllText(path, null);
         }
 
+        /// <summary>
+        /// Replaces invalid file name characters with '_'
+        /// </summary>
+        public static string ReplaceInvalidFileNameChars(string fileName)
+        {
+            var result = new StringBuilder();
+            var invalidChars = Path.GetInvalidFileNameChars();
+
+            var current = 0; // Current index
+            while (current < fileName?.Length)
+            {
+                var next = fileName.IndexOfAny(invalidChars, current);
+                if (next >= 0)
+                {
+                    result.Append(fileName.Substring(current, next - current));
+                    result.Append('_');
+                    current = next + 1;
+                }
+                else
+                {
+                    result.Append(fileName.Substring(current));
+                    break;
+                }
+            }
+
+            return result.ToString();
+        }
+
         /// <summary>
         /// Recursively enumerates a directory without following directory reparse points.
         /// </summary>
diff --git a/src/Runner.Worker/DiagnosticLogManager.cs b/src/Runner.Worker/DiagnosticLogManager.cs
index 261689b5f3f..afc811b15e4 100644
--- a/src/Runner.Worker/DiagnosticLogManager.cs
+++ b/src/Runner.Worker/DiagnosticLogManager.cs
@@ -91,13 +91,13 @@ public void UploadDiagnosticLogs(IExecutionContext executionContext,
             string phaseName = executionContext.Global.Variables.System_PhaseDisplayName ?? "UnknownPhaseName";
 
             // zip the files
-            string diagnosticsZipFileName = $"{buildName}-{phaseName}.zip";
+            string diagnosticsZipFileName = $"{buildName}-{IOUtil.ReplaceInvalidFileNameChars(phaseName)}.zip";
             string diagnosticsZipFilePath = Path.Combine(supportRootFolder, diagnosticsZipFileName);
             ZipFile.CreateFromDirectory(supportFilesFolder, diagnosticsZipFilePath);
 
             // upload the json metadata file
             executionContext.Debug("Uploading diagnostic metadata file.");
-            string metadataFileName = $"diagnostics-{buildName}-{phaseName}.json";
+            string metadataFileName = $"diagnostics-{buildName}-{IOUtil.ReplaceInvalidFileNameChars(phaseName)}.json";
             string metadataFilePath = Path.Combine(supportFilesFolder, metadataFileName);
             string phaseResult = GetTaskResultAsString(executionContext.Result);
 
diff --git a/src/Test/L0/Util/IOUtilL0.cs b/src/Test/L0/Util/IOUtilL0.cs
index 08d3e9773d1..e9478dff210 100644
--- a/src/Test/L0/Util/IOUtilL0.cs
+++ b/src/Test/L0/Util/IOUtilL0.cs
@@ -960,6 +960,33 @@ public void LoadObject_ThrowsOnRequiredLoadObject()
             }
         }
 
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Common")]
+        public void ReplaceInvalidFileNameChars()
+        {
+            Assert.Equal(string.Empty, IOUtil.ReplaceInvalidFileNameChars(null));
+            Assert.Equal(string.Empty, IOUtil.ReplaceInvalidFileNameChars(string.Empty));
+            Assert.Equal("hello.txt", IOUtil.ReplaceInvalidFileNameChars("hello.txt"));
+#if OS_WINDOWS
+            // Refer https://github.com/dotnet/runtime/blob/ce84f1d8a3f12711bad678a33efbc37b461f684f/src/libraries/System.Private.CoreLib/src/System/IO/Path.Windows.cs#L15
+            Assert.Equal(
+                "1_ 2_ 3_ 4_ 5_ 6_ 7_ 8_ 9_ 10_ 11_ 12_ 13_ 14_ 15_ 16_ 17_ 18_ 19_ 20_ 21_ 22_ 23_ 24_ 25_ 26_ 27_ 28_ 29_ 30_ 31_ 32_ 33_ 34_ 35_ 36_ 37_ 38_ 39_ 40_ 41_",
+                IOUtil.ReplaceInvalidFileNameChars($"1\" 2< 3> 4| 5\0 6{(char)1} 7{(char)2} 8{(char)3} 9{(char)4} 10{(char)5} 11{(char)6} 12{(char)7} 13{(char)8} 14{(char)9} 15{(char)10} 16{(char)11} 17{(char)12} 18{(char)13} 19{(char)14} 20{(char)15} 21{(char)16} 22{(char)17} 23{(char)18} 24{(char)19} 25{(char)20} 26{(char)21} 27{(char)22} 28{(char)23} 29{(char)24} 30{(char)25} 31{(char)26} 32{(char)27} 33{(char)28} 34{(char)29} 35{(char)30} 36{(char)31} 37: 38* 39? 40\\ 41/"));
+#else
+            // Refer https://github.com/dotnet/runtime/blob/ce84f1d8a3f12711bad678a33efbc37b461f684f/src/libraries/System.Private.CoreLib/src/System/IO/Path.Unix.cs#L12
+            Assert.Equal("1_ 2_", IOUtil.ReplaceInvalidFileNameChars("1\0 2/"));
+#endif
+            Assert.Equal("_leading", IOUtil.ReplaceInvalidFileNameChars("/leading"));
+            Assert.Equal("__consecutive leading", IOUtil.ReplaceInvalidFileNameChars("//consecutive leading"));
+            Assert.Equal("trailing_", IOUtil.ReplaceInvalidFileNameChars("trailing/"));
+            Assert.Equal("consecutive trailing__", IOUtil.ReplaceInvalidFileNameChars("consecutive trailing//"));
+            Assert.Equal("middle_middle", IOUtil.ReplaceInvalidFileNameChars("middle/middle"));
+            Assert.Equal("consecutive middle__consecutive middle", IOUtil.ReplaceInvalidFileNameChars("consecutive middle//consecutive middle"));
+            Assert.Equal("_leading_middle_trailing_", IOUtil.ReplaceInvalidFileNameChars("/leading/middle/trailing/"));
+            Assert.Equal("__consecutive leading__consecutive middle__consecutive trailing__", IOUtil.ReplaceInvalidFileNameChars("//consecutive leading//consecutive middle//consecutive trailing//"));
+        }
+
         private static async Task CreateDirectoryReparsePoint(IHostContext context, string link, string target)
         {
 #if OS_WINDOWS