diff --git a/src/harness/fourslash.ts b/src/harness/fourslash.ts
index 07aacf3c8a7..aa3097debad 100644
--- a/src/harness/fourslash.ts
+++ b/src/harness/fourslash.ts
@@ -2427,6 +2427,16 @@ namespace FourSlash {
             }
         }
 
+        public verifyIsInMultiLineComment(negative: boolean) {
+            const expected = !negative;
+            const position = this.currentCaretPosition;
+            const fileName = this.activeFile.fileName;
+            const actual = this.languageService.getIsInMultiLineComment(fileName, position);
+            if (expected !== actual) {
+                this.raiseError(`verifyIsInDocComment failed: at position '${position}' in '${fileName}', expected '${expected}'.`);
+            }
+        }
+
         private clarifyNewlines(str: string) {
             return str.replace(/\r?\n/g, lineEnding => {
                 const representation = lineEnding === "\r\n" ? "CRLF" : "LF";
@@ -3577,6 +3587,10 @@ namespace FourSlashInterface {
             this.state.verifyCodeFixAvailable(this.negative);
         }
 
+        public isInMultiLineComment() {
+            this.state.verifyIsInMultiLineComment(this.negative);
+        }
+
         public applicableRefactorAvailableAtMarker(markerName: string) {
             this.state.verifyApplicableRefactorAvailableAtMarker(this.negative, markerName);
         }
diff --git a/src/harness/harnessLanguageService.ts b/src/harness/harnessLanguageService.ts
index 7aefb0f3a1f..c67dde5f67b 100644
--- a/src/harness/harnessLanguageService.ts
+++ b/src/harness/harnessLanguageService.ts
@@ -483,6 +483,9 @@ namespace Harness.LanguageService {
         getDocCommentTemplateAtPosition(fileName: string, position: number): ts.TextInsertion {
             return unwrapJSONCallResult(this.shim.getDocCommentTemplateAtPosition(fileName, position));
         }
+        getIsInMultiLineComment(fileName: string, position: number): boolean {
+            return unwrapJSONCallResult(this.shim.getIsInMultiLineComment(fileName, position));
+        }
         isValidBraceCompletionAtPosition(fileName: string, position: number, openingBrace: number): boolean {
             return unwrapJSONCallResult(this.shim.isValidBraceCompletionAtPosition(fileName, position, openingBrace));
         }
diff --git a/src/server/client.ts b/src/server/client.ts
index aca52422e44..69727a18e60 100644
--- a/src/server/client.ts
+++ b/src/server/client.ts
@@ -672,6 +672,10 @@ namespace ts.server {
             return notImplemented();
         }
 
+        getIsInMultiLineComment(_fileName: string, _position: number): boolean {
+            return notImplemented();
+        }
+
         isValidBraceCompletionAtPosition(_fileName: string, _position: number, _openingBrace: number): boolean {
             return notImplemented();
         }
diff --git a/src/server/protocol.ts b/src/server/protocol.ts
index 4e474edd0c4..1cfe617ca72 100644
--- a/src/server/protocol.ts
+++ b/src/server/protocol.ts
@@ -85,6 +85,7 @@ namespace ts.server.protocol {
         TodoComments = "todoComments",
         Indentation = "indentation",
         DocCommentTemplate = "docCommentTemplate",
+        IsInMultiLineComment = "isInMultiLineComment",
         /* @internal */
         CompilerOptionsDiagnosticsFull = "compilerOptionsDiagnostics-full",
         /* @internal */
@@ -238,6 +239,20 @@ namespace ts.server.protocol {
         body?: TodoComment[];
     }
 
+    /**
+     * A request to determine if the caret is inside a multi-line comment.
+     */
+    export interface IsInMultiLineCommentRequest extends FileLocationRequest {
+        command: CommandTypes.IsInMultiLineComment;
+    }
+
+    /**
+     * Response for TodoCommentRequest request.
+     */
+    export interface IsInMultiLineCommentResponse extends Response {
+        body?: { isInMultiLineComment: boolean };
+    }
+
     /**
      * Request to obtain outlining spans in file.
      */
diff --git a/src/server/session.ts b/src/server/session.ts
index 6ec234952db..abebdb5fae9 100644
--- a/src/server/session.ts
+++ b/src/server/session.ts
@@ -961,6 +961,13 @@ namespace ts.server {
             return project.getLanguageService(/*ensureSynchronized*/ false).getDocCommentTemplateAtPosition(file, position);
         }
 
+        private getIsInMultiLineComment(args: protocol.FileLocationRequestArgs) {
+            const { file, project } = this.getFileAndProjectWithoutRefreshingInferredProjects(args);
+            const scriptInfo = project.getScriptInfoForNormalizedPath(file);
+            const position = this.getPosition(args, scriptInfo);
+            return project.getLanguageService(/*ensureSynchronized*/ false).getIsInMultiLineComment(file, position);
+        }
+
         private getIndentation(args: protocol.IndentationRequestArgs) {
             const { file, project } = this.getFileAndProjectWithoutRefreshingInferredProjects(args);
             const position = this.getPosition(args, project.getScriptInfoForNormalizedPath(file));
@@ -1694,6 +1701,9 @@ namespace ts.server {
             [CommandNames.DocCommentTemplate]: (request: protocol.DocCommentTemplateRequest) => {
                 return this.requiredResponse(this.getDocCommentTemplate(request.arguments));
             },
+            [CommandNames.IsInMultiLineComment]: (request: protocol.IsInMultiLineCommentRequest) => {
+                return this.requiredResponse(this.getIsInMultiLineComment(request.arguments));
+            },
             [CommandNames.Format]: (request: protocol.FormatRequest) => {
                 return this.requiredResponse(this.getFormattingEditsForRange(request.arguments));
             },
diff --git a/src/services/services.ts b/src/services/services.ts
index 21c756a9acc..8da654140e0 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -1789,6 +1789,16 @@ namespace ts {
             return JsDoc.getDocCommentTemplateAtPosition(getNewLineOrDefaultFromHost(host), syntaxTreeCache.getCurrentSourceFile(fileName), position);
         }
 
+        function getIsInMultiLineComment(_fileName: string, position: number): boolean {
+            const sourceFile = syntaxTreeCache.getCurrentSourceFile(_fileName);
+            const token = getTokenAtPosition(sourceFile, position, /*includeJsDocComment*/ true);
+            const _triviaWidth = token.getLeadingTriviaWidth(sourceFile); _triviaWidth;
+            const _text = token.getText(sourceFile); _text;
+            const _fullText = token.getFullText(sourceFile); _fullText;
+            // TODO: distinguish multi-line and single line comments...
+            return token.getFullStart() <= position && position < token.getStart(sourceFile, /*includeJsDocComment*/ false);
+        }
+
         function isValidBraceCompletionAtPosition(fileName: string, position: number, openingBrace: number): boolean {
             // '<' is currently not supported, figuring out if we're in a Generic Type vs. a comparison is too
             // expensive to do during typing scenarios
@@ -2039,6 +2049,7 @@ namespace ts {
             getFormattingEditsForDocument,
             getFormattingEditsAfterKeystroke,
             getDocCommentTemplateAtPosition,
+            getIsInMultiLineComment,
             isValidBraceCompletionAtPosition,
             getCodeFixesAtPosition,
             getEmitOutput,
diff --git a/src/services/shims.ts b/src/services/shims.ts
index 498c1834a60..3ce553d552e 100644
--- a/src/services/shims.ts
+++ b/src/services/shims.ts
@@ -247,6 +247,11 @@ namespace ts {
          */
         getDocCommentTemplateAtPosition(fileName: string, position: number): string;
 
+        /**
+         * Returns JSON-encoded value of the type TextInsertion.
+         */
+        getIsInMultiLineComment(fileName: string, position: number): string;
+
         /**
          * Returns JSON-encoded boolean to indicate whether we should support brace location
          * at the current position.
@@ -935,6 +940,13 @@ namespace ts {
             );
         }
 
+        public getIsInMultiLineComment(fileName: string, position: number): string {
+            return this.forwardJSONCall(
+                `getIsInMultiLineComment('${fileName}', ${position})`,
+                () => this.languageService.getIsInMultiLineComment(fileName, position)
+            );
+        }
+
         /// NAVIGATE TO
 
         /** Return a list of symbols that are interesting to navigate to */
diff --git a/src/services/types.ts b/src/services/types.ts
index e042276e650..62d2db1b65c 100644
--- a/src/services/types.ts
+++ b/src/services/types.ts
@@ -257,6 +257,7 @@ namespace ts {
         getFormattingEditsAfterKeystroke(fileName: string, position: number, key: string, options: FormatCodeOptions | FormatCodeSettings): TextChange[];
 
         getDocCommentTemplateAtPosition(fileName: string, position: number): TextInsertion;
+        getIsInMultiLineComment(fileName: string, position: number): boolean;
 
         isValidBraceCompletionAtPosition(fileName: string, position: number, openingBrace: number): boolean;
 
diff --git a/tests/cases/fourslash/fourslash.ts b/tests/cases/fourslash/fourslash.ts
index 3e80b005625..3984a074fd9 100644
--- a/tests/cases/fourslash/fourslash.ts
+++ b/tests/cases/fourslash/fourslash.ts
@@ -150,6 +150,7 @@ declare namespace FourSlashInterface {
         implementationListIsEmpty(): void;
         isValidBraceCompletionAtPosition(openingBrace?: string): void;
         codeFixAvailable(): void;
+        isInMultiLineComment(): void;
         applicableRefactorAvailableAtMarker(markerName: string): void;
         codeFixDiagnosticsAvailableAtMarkers(markerNames: string[], diagnosticCode?: number): void;
         applicableRefactorAvailableForRange(): void;
diff --git a/tests/cases/fourslash/isInMultiLineComment.ts b/tests/cases/fourslash/isInMultiLineComment.ts
new file mode 100644
index 00000000000..4d6c8d6af1a
--- /dev/null
+++ b/tests/cases/fourslash/isInMultiLineComment.ts
@@ -0,0 +1,6 @@
+/// <reference path="fourslash.ts" />
+
+//// /* blach /*m0*/ */ let x = 10;
+
+goTo.marker("m0");
+verify.isInMultiLineComment();
\ No newline at end of file