diff --git a/src/server/session.ts b/src/server/session.ts
index e6c4c33a53d0d..14ad20d7aaeac 100644
--- a/src/server/session.ts
+++ b/src/server/session.ts
@@ -336,16 +336,23 @@ namespace ts.server {
     function combineProjectOutputForReferences(projects: Projects, defaultProject: Project, initialLocation: sourcemaps.SourceMappableLocation, projectService: ProjectService): ReadonlyArray<ReferencedSymbol> {
         const outputs: ReferencedSymbol[] = [];
 
-        combineProjectOutputWorker<sourcemaps.SourceMappableLocation>(projects, defaultProject, initialLocation, projectService, ({ project, location }, tryAddToTodo) => {
+        combineProjectOutputWorker<sourcemaps.SourceMappableLocation>(projects, defaultProject, initialLocation, projectService, ({ project, location }, getMappedLocation) => {
             for (const outputReferencedSymbol of project.getLanguageService().findReferences(location.fileName, location.position) || emptyArray) {
-                let symbolToAddTo = find(outputs, o => documentSpansEqual(o.definition, outputReferencedSymbol.definition));
+                const mappedDefinitionFile = getMappedLocation(project, documentSpanLocation(outputReferencedSymbol.definition));
+                const definition: ReferencedSymbolDefinitionInfo = mappedDefinitionFile === undefined ? outputReferencedSymbol.definition : {
+                    ...outputReferencedSymbol.definition,
+                    textSpan: createTextSpan(mappedDefinitionFile.position, outputReferencedSymbol.definition.textSpan.length),
+                    fileName: mappedDefinitionFile.fileName,
+                };
+                let symbolToAddTo = find(outputs, o => documentSpansEqual(o.definition, definition));
                 if (!symbolToAddTo) {
-                    symbolToAddTo = { definition: outputReferencedSymbol.definition, references: [] };
+                    symbolToAddTo = { definition, references: [] };
                     outputs.push(symbolToAddTo);
                 }
 
                 for (const ref of outputReferencedSymbol.references) {
-                    if (!contains(symbolToAddTo.references, ref, documentSpansEqual) && !tryAddToTodo(project, documentSpanLocation(ref))) {
+                    // If it's in a mapped file, that is added to the todo list by `getMappedLocation`.
+                    if (!contains(symbolToAddTo.references, ref, documentSpansEqual) && !getMappedLocation(project, documentSpanLocation(ref))) {
                         symbolToAddTo.references.push(ref);
                     }
                 }
@@ -373,12 +380,17 @@ namespace ts.server {
         }
     }
 
+    type CombineProjectOutputCallback<TLocation extends sourcemaps.SourceMappableLocation | undefined> = (
+        where: ProjectAndLocation<TLocation>,
+        getMappedLocation: (project: Project, location: sourcemaps.SourceMappableLocation) => sourcemaps.SourceMappableLocation | undefined,
+    ) => void;
+
     function combineProjectOutputWorker<TLocation extends sourcemaps.SourceMappableLocation | undefined>(
         projects: Projects,
         defaultProject: Project,
         initialLocation: TLocation,
         projectService: ProjectService,
-        cb: (where: ProjectAndLocation<TLocation>, getMappedLocation: (project: Project, location: sourcemaps.SourceMappableLocation) => boolean) => void,
+        cb: CombineProjectOutputCallback<TLocation>,
         getDefinition: (() => sourcemaps.SourceMappableLocation | undefined) | undefined,
     ): void {
         let toDo: ProjectAndLocation<TLocation>[] | undefined;
@@ -417,13 +429,13 @@ namespace ts.server {
         projectService: ProjectService,
         toDo: ProjectAndLocation<TLocation>[] | undefined,
         seenProjects: Map<true>,
-        cb: (where: ProjectAndLocation<TLocation>, getMappedLocation: (project: Project, location: sourcemaps.SourceMappableLocation) => boolean) => void,
+        cb: CombineProjectOutputCallback<TLocation>,
     ): ProjectAndLocation<TLocation>[] | undefined {
         if (projectAndLocation.project.getCancellationToken().isCancellationRequested()) return undefined; // Skip rest of toDo if cancelled
         cb(projectAndLocation, (project, location) => {
             seenProjects.set(projectAndLocation.project.projectName, true);
             const originalLocation = projectService.getOriginalLocationEnsuringConfiguredProject(project, location);
-            if (!originalLocation) return false;
+            if (!originalLocation) return undefined;
 
             const originalScriptInfo = projectService.getScriptInfo(originalLocation.fileName)!;
             toDo = toDo || [];
@@ -437,7 +449,7 @@ namespace ts.server {
                     for (const symlinkedProject of symlinkedProjects) addToTodo({ project: symlinkedProject, location: originalLocation as TLocation }, toDo!, seenProjects);
                 });
             }
-            return true;
+            return originalLocation;
         });
         return toDo;
     }
diff --git a/src/testRunner/unittests/tsserverProjectSystem.ts b/src/testRunner/unittests/tsserverProjectSystem.ts
index ed130f6772b4f..4d9b74a38dec3 100644
--- a/src/testRunner/unittests/tsserverProjectSystem.ts
+++ b/src/testRunner/unittests/tsserverProjectSystem.ts
@@ -3491,7 +3491,7 @@ namespace ts.projectSystem {
             host.checkTimeoutQueueLength(2); // Update configured project and projects for open file
             checkProjectActualFiles(services.configuredProjects.get(config.path)!, filesWithFileA.map(f => f.path));
 
-           // host.fileExists = originalFileExists;
+            // host.fileExists = originalFileExists;
             openFile(fileSubA);
             // This should create inferred project since fileSubA not on the disk
             checkProjectActualFiles(services.configuredProjects.get(config.path)!, mapDefined(filesWithFileA, f => f === fileA ? undefined : f.path));
@@ -3672,7 +3672,7 @@ namespace ts.projectSystem {
                 path: `${projectRoot}/app1/tsconfig.json`,
                 content: JSON.stringify({
                     files: ["app.ts", "../core/core.ts"],
-                    compilerOptions: { outFile : "build/output.js" },
+                    compilerOptions: { outFile: "build/output.js" },
                     compileOnSave: true
                 })
             };
@@ -6778,9 +6778,9 @@ namespace ts.projectSystem {
                         fileName: "/a.1.ts",
                         textChanges: [
                             {
-                              start: { line: 0, offset: 0 },
-                              end: { line: 0, offset: 0 },
-                              newText: "export const a = 0;",
+                                start: { line: 0, offset: 0 },
+                                end: { line: 0, offset: 0 },
+                                newText: "export const a = 0;",
                             },
                         ],
                     }
@@ -8672,7 +8672,7 @@ new C();`
             }));
             checkWatchedDirectories(host, [], /*recursive*/ false);
             checkWatchedDirectories(host, arrayFrom(expectedRecursiveDirectories.keys()), /*recursive*/ true);
-       }
+        }
 
         describe("from files in same folder", () => {
             function getFiles(fileContent: string) {
@@ -9750,7 +9750,7 @@ declare class TestLib {
         function verifyATsConfigOriginalProject(session: TestSession) {
             checkNumberOfProjects(session.getProjectService(), { inferredProjects: 1, configuredProjects: 1 });
             verifyInferredProjectUnchanged(session);
-             verifyATsConfigProject(session);
+            verifyATsConfigProject(session);
             // Close user file should close all the projects
             closeFilesForSession([userTs], session);
             verifyOnlyOrphanInferredProject(session);
@@ -9900,11 +9900,12 @@ declare class TestLib {
             verifyATsConfigWhenOpened(session);
         });
 
+        interface ReferencesFullRequest extends protocol.FileLocationRequest { readonly command: protocol.CommandTypes.ReferencesFull; }
+        interface ReferencesFullResponse extends protocol.Response { readonly body: ReadonlyArray<ReferencedSymbol>; }
+
         it("findAllReferencesFull", () => {
             const session = makeSampleProjects();
 
-            interface ReferencesFullRequest extends protocol.FileLocationRequest { command: protocol.CommandTypes.ReferencesFull; }
-            interface ReferencesFullResponse extends protocol.Response { body: ReadonlyArray<ReferencedSymbol>; }
             const responseFull = executeSessionRequest<ReferencesFullRequest, ReferencesFullResponse>(session, protocol.CommandTypes.ReferencesFull, protocolFileLocationFromSubstring(userTs, "fnA()"));
 
             function fnAVoid(kind: SymbolDisplayPartKind): SymbolDisplayPart[] {
@@ -9961,6 +9962,67 @@ declare class TestLib {
             verifyATsConfigOriginalProject(session);
         });
 
+        it("findAllReferencesFull definition is in mapped file", () => {
+            const aTs: File = { path: "/a/a.ts", content: `function f() {}` };
+            const aTsconfig: File = {
+                path: "/a/tsconfig.json",
+                content: JSON.stringify({ compilerOptions: { declaration: true, declarationMap: true, outFile: "../bin/a.js" } }),
+            };
+            const bTs: File = { path: "/b/b.ts", content: `f();` };
+            const bTsconfig: File = { path: "/b/tsconfig.json", content: JSON.stringify({ references: [{ path: "../a" }] }) };
+            const aDts: File = { path: "/bin/a.d.ts", content: `declare function f(): void;\n//# sourceMappingURL=a.d.ts.map` };
+            const aDtsMap: File = {
+                path: "/bin/a.d.ts.map",
+                content: JSON.stringify({ version: 3, file: "a.d.ts", sourceRoot: "", sources: ["../a/a.ts"], names: [], mappings: "AAAA,iBAAS,CAAC,SAAK" }),
+            };
+
+            const session = createSession(createServerHost([aTs, aTsconfig, bTs, bTsconfig, aDts, aDtsMap]));
+            checkDeclarationFiles(aTs, session, [aDtsMap, aDts]);
+            openFilesForSession([bTs], session);
+            checkNumberOfProjects(session.getProjectService(), { configuredProjects: 1 });
+
+            const responseFull = executeSessionRequest<ReferencesFullRequest, ReferencesFullResponse>(session, protocol.CommandTypes.ReferencesFull, protocolFileLocationFromSubstring(bTs, "f()"));
+
+            assert.deepEqual<ReadonlyArray<ReferencedSymbol>>(responseFull, [
+                {
+                    definition: {
+                        containerKind: ScriptElementKind.unknown,
+                        containerName: "",
+                        displayParts: [
+                            keywordPart(SyntaxKind.FunctionKeyword),
+                            spacePart(),
+                            displayPart("f", SymbolDisplayPartKind.functionName),
+                            punctuationPart(SyntaxKind.OpenParenToken),
+                            punctuationPart(SyntaxKind.CloseParenToken),
+                            punctuationPart(SyntaxKind.ColonToken),
+                            spacePart(),
+                            keywordPart(SyntaxKind.VoidKeyword),
+                        ],
+                        fileName: aTs.path,
+                        kind: ScriptElementKind.functionElement,
+                        name: "function f(): void",
+                        textSpan: { start: 9, length: 1 },
+                    },
+                    references: [
+                        {
+                            fileName: bTs.path,
+                            isDefinition: false,
+                            isInString: undefined,
+                            isWriteAccess: false,
+                            textSpan: { start: 0, length: 1 },
+                        },
+                        {
+                            fileName: aTs.path,
+                            isDefinition: true,
+                            isInString: undefined,
+                            isWriteAccess: true,
+                            textSpan: { start: 9, length: 1 },
+                        },
+                    ],
+                }
+            ]);
+        });
+
         it("findAllReferences -- target does not exist", () => {
             const session = makeSampleProjects();