diff --git a/src/loaders/js.ts b/src/loaders/js.ts
index e7e79fe..5cdf94d 100644
--- a/src/loaders/js.ts
+++ b/src/loaders/js.ts
@@ -2,6 +2,7 @@ import { transform } from "esbuild";
 import jiti from "jiti";
 
 import type { Loader, LoaderResult } from "../loader";
+import { getOutputExtension } from "../utils";
 
 const DECLARATION_RE = /\.d\.[cm]?ts$/;
 const CM_LETTER_RE = /(?<=\.)(c|m)(?=[jt]s$)/;
@@ -55,10 +56,7 @@ export const jsLoader: Loader = async (input, { options }) => {
       .replace("module.exports = void 0;", "");
   }
 
-  let extension = isCjs ? ".js" : ".mjs"; // TODO: Default to .cjs in next major version
-  if (options.ext) {
-    extension = options.ext.startsWith(".") ? options.ext : `.${options.ext}`;
-  }
+  const extension = getOutputExtension(options);
 
   output.push({
     contents,
diff --git a/src/utils/dts.ts b/src/utils/dts.ts
index 279cac1..87b8fa6 100644
--- a/src/utils/dts.ts
+++ b/src/utils/dts.ts
@@ -3,6 +3,7 @@ import { findStaticImports, findExports, findTypeExports } from "mlly";
 import { resolve } from "pathe";
 import type { TSConfig } from "pkg-types";
 import type { MkdistOptions } from "../make";
+import { getOutputExtension } from "./index";
 
 export async function normalizeCompilerOptions(
   _options: TSConfig["compilerOptions"],
@@ -60,7 +61,10 @@ export function extractDeclarations(
     const dtsFilename = filename.replace(JSX_EXT_RE, ".d.$1ts");
     let contents = vfs.get(dtsFilename) || "";
     if (opts?.addRelativeDeclarationExtensions) {
-      const ext = filename.match(JS_EXT_RE)?.[0].replace(/ts$/, "js") || ".js";
+      const srcExt =
+        filename.match(JS_EXT_RE)?.[0].replace(/ts$/, "js") || ".js";
+      const ext = getOutputExtension(opts);
+
       const imports = findStaticImports(contents);
       const exports = findExports(contents);
       const typeExports = findTypeExports(contents);
@@ -69,7 +73,8 @@ export function extractDeclarations(
           continue;
         }
         const srcPath = resolve(filename, "..", spec.specifier);
-        const srcDtsPath = srcPath + ext.replace(JS_EXT_RE, ".d.$1ts");
+        const srcDtsPath = srcPath + srcExt.replace(JS_EXT_RE, ".d.$1ts");
+
         let specifier = spec.specifier;
         try {
           if (!vfs.get(srcDtsPath)) {
diff --git a/src/utils/index.ts b/src/utils/index.ts
new file mode 100644
index 0000000..0c6f220
--- /dev/null
+++ b/src/utils/index.ts
@@ -0,0 +1,10 @@
+import type { MkdistOptions } from "../make";
+
+export function getOutputExtension(options: MkdistOptions) {
+  const isCjs = options.format === "cjs";
+  let ext = isCjs ? ".js" : ".mjs"; // TODO: Default to .cjs in next major version
+  if (options.ext) {
+    ext = options.ext.startsWith(".") ? options.ext : `.${options.ext}`;
+  }
+  return ext;
+}
diff --git a/test/index.test.ts b/test/index.test.ts
index 854fc2e..29e98db 100644
--- a/test/index.test.ts
+++ b/test/index.test.ts
@@ -156,6 +156,168 @@ describe("mkdist", () => {
       "manual declaration",
     );
 
+    expect(await readFile(resolve(rootDir, "dist/star/index.d.ts"), "utf8"))
+      .toMatchInlineSnapshot(`
+        "export * from "./other.mjs";
+        export type { Other } from "./other.mjs";
+        "
+      `);
+
+    expect(await readFile(resolve(rootDir, "dist/dir-export.d.ts"), "utf8"))
+      .toMatchInlineSnapshot(`
+        "export { default as bar } from "./bar.mjs";
+        export * from "./star/index.mjs";
+        "
+      `);
+
+    expect(
+      await readFile(resolve(rootDir, "dist/bar/esm.d.mts"), "utf8"),
+    ).toMatch("declare");
+
+    expect(
+      await readFile(resolve(rootDir, "dist/components/index.d.ts"), "utf8"),
+    ).toMatchInlineSnapshot(`
+      "export * as jsx from "./jsx.jsx.mjs";
+      export * as tsx from "./tsx.tsx.mjs";
+      export * as blank from "./blank.vue.mjs";
+      export * as scriptSetupTS from "./script-setup-ts.vue.mjs";
+      export * as scriptMultiBlock from "./script-multi-block.vue.mjs";
+      export * as ts from "./ts.vue.mjs";
+      "
+    `);
+
+    expect(
+      await readFile(resolve(rootDir, "dist/components/ts.vue.d.ts"), "utf8"),
+    ).toMatchInlineSnapshot(`
+      "declare const _default: import("vue").DefineComponent<{}, {}, {
+          test: string;
+          str: "test";
+      }, {}, {}, import("vue").ComponentOptionsMixin, import("vue").ComponentOptionsMixin, {}, string, import("vue").PublicProps, Readonly<{}> & Readonly<{}>, {}, {}, {}, {}, string, import("vue").ComponentProvideOptions, true, {}, any>;
+      export default _default;
+      "
+    `);
+
+    expect(
+      await readFile(
+        resolve(rootDir, "dist/components/blank.vue.d.ts"),
+        "utf8",
+      ),
+    ).toMatchInlineSnapshot(`
+      "declare const _default: import("vue").DefineComponent<{}, {}, {}, {}, {}, import("vue").ComponentOptionsMixin, import("vue").ComponentOptionsMixin, {}, string, import("vue").PublicProps, Readonly<{}> & Readonly<{}>, {}, {}, {}, {}, string, import("vue").ComponentProvideOptions, true, {}, any>;
+      export default _default;
+      "
+    `);
+
+    expect(
+      await readFile(
+        resolve(rootDir, "dist/components/script-multi-block.vue.d.ts"),
+        "utf8",
+      ),
+    ).toMatchInlineSnapshot(`
+      "interface MyComponentProps {
+          msg: string;
+      }
+      declare const _default: import("vue").DefineComponent<import("vue").ExtractPropTypes<__VLS_TypePropsToOption<MyComponentProps>>, {}, {}, {}, {}, import("vue").ComponentOptionsMixin, import("vue").ComponentOptionsMixin, {}, string, import("vue").PublicProps, Readonly<import("vue").ExtractPropTypes<__VLS_TypePropsToOption<MyComponentProps>>> & Readonly<{}>, {}, {}, {}, {}, string, import("vue").ComponentProvideOptions, true, {}, any>;
+      export default _default;
+      type __VLS_NonUndefinedable<T> = T extends undefined ? never : T;
+      type __VLS_TypePropsToOption<T> = {
+          [K in keyof T]-?: {} extends Pick<T, K> ? {
+              type: import('vue').PropType<__VLS_NonUndefinedable<T[K]>>;
+          } : {
+              type: import('vue').PropType<T[K]>;
+              required: true;
+          };
+      };
+      "
+    `);
+
+    expect(
+      await readFile(
+        resolve(rootDir, "dist/components/script-setup-ts.vue.d.ts"),
+        "utf8",
+      ),
+    ).toMatchInlineSnapshot(`
+      "import { Color } from "#prop-types";
+      type __VLS_Props = {
+          msg: string;
+          color: Color;
+      };
+      declare const _default: import("vue").DefineComponent<import("vue").ExtractPropTypes<__VLS_TypePropsToOption<__VLS_Props>>, {}, {}, {}, {}, import("vue").ComponentOptionsMixin, import("vue").ComponentOptionsMixin, {}, string, import("vue").PublicProps, Readonly<import("vue").ExtractPropTypes<__VLS_TypePropsToOption<__VLS_Props>>> & Readonly<{}>, {}, {}, {}, {}, string, import("vue").ComponentProvideOptions, true, {}, any>;
+      export default _default;
+      type __VLS_NonUndefinedable<T> = T extends undefined ? never : T;
+      type __VLS_TypePropsToOption<T> = {
+          [K in keyof T]-?: {} extends Pick<T, K> ? {
+              type: import('vue').PropType<__VLS_NonUndefinedable<T[K]>>;
+          } : {
+              type: import('vue').PropType<T[K]>;
+              required: true;
+          };
+      };
+      "
+    `);
+  }, 50_000);
+
+  it("mkdist (emit types) [js]", async () => {
+    const rootDir = resolve(__dirname, "fixture");
+    const { writtenFiles } = await mkdist({
+      rootDir,
+      declaration: true,
+      addRelativeDeclarationExtensions: true,
+      ext: "js",
+    });
+    expect(writtenFiles.sort()).toEqual(
+      [
+        "dist/README.md",
+        "dist/bar.d.ts",
+        "dist/bar.js",
+        "dist/demo.css",
+        "dist/dir-export.d.ts",
+        "dist/dir-export.js",
+        "dist/foo.js",
+        "dist/foo.d.ts",
+        "dist/index.js",
+        "dist/index.d.ts",
+        "dist/star/index.js",
+        "dist/star/index.d.ts",
+        "dist/star/other.js",
+        "dist/star/other.d.ts",
+        "dist/types.d.ts",
+        "dist/components/index.js",
+        "dist/components/index.d.ts",
+        "dist/components/blank.vue",
+        "dist/components/blank.vue.d.ts",
+        "dist/components/js.vue",
+        "dist/components/js.vue.d.ts",
+        "dist/components/script-multi-block.vue",
+        "dist/components/script-multi-block.vue.d.ts",
+        "dist/components/script-setup-ts.vue",
+        "dist/components/script-setup-ts.vue.d.ts",
+        "dist/components/ts.vue",
+        "dist/components/ts.vue.d.ts",
+        "dist/components/jsx.js",
+        "dist/components/tsx.js",
+        "dist/components/jsx.d.ts",
+        "dist/components/tsx.d.ts",
+        "dist/bar/index.js",
+        "dist/bar/index.d.ts",
+        "dist/bar/esm.js",
+        "dist/bar/esm.d.mts",
+        "dist/ts/test1.js",
+        "dist/ts/test2.js",
+        "dist/ts/test1.d.mts",
+        "dist/ts/test2.d.cts",
+        "dist/nested.css",
+        "dist/prop-types/index.js",
+        "dist/prop-types/index.d.ts",
+      ]
+        .map((f) => resolve(rootDir, f))
+        .sort(),
+    );
+
+    expect(await readFile(resolve(rootDir, "dist/foo.d.ts"), "utf8")).toMatch(
+      "manual declaration",
+    );
+
     expect(await readFile(resolve(rootDir, "dist/star/index.d.ts"), "utf8"))
       .toMatchInlineSnapshot(`
         "export * from "./other.js";
@@ -589,8 +751,8 @@ describe("mkdist with vue-tsc v1", () => {
 
     expect(await readFile(resolve(rootDir, "dist/star/index.d.ts"), "utf8"))
       .toMatchInlineSnapshot(`
-        "export * from "./other.js";
-        export type { Other } from "./other.js";
+        "export * from "./other.mjs";
+        export type { Other } from "./other.mjs";
         "
       `);
     expect(
@@ -600,12 +762,12 @@ describe("mkdist with vue-tsc v1", () => {
     expect(
       await readFile(resolve(rootDir, "dist/components/index.d.ts"), "utf8"),
     ).toMatchInlineSnapshot(`
-      "export * as jsx from "./jsx.jsx.js";
-      export * as tsx from "./tsx.tsx.js";
-      export * as blank from "./blank.vue.js";
-      export * as scriptSetupTS from "./script-setup-ts.vue.js";
-      export * as scriptMultiBlock from "./script-multi-block.vue.js";
-      export * as ts from "./ts.vue.js";
+      "export * as jsx from "./jsx.jsx.mjs";
+      export * as tsx from "./tsx.tsx.mjs";
+      export * as blank from "./blank.vue.mjs";
+      export * as scriptSetupTS from "./script-setup-ts.vue.mjs";
+      export * as scriptMultiBlock from "./script-multi-block.vue.mjs";
+      export * as ts from "./ts.vue.mjs";
       "
     `);
 
@@ -846,8 +1008,8 @@ describe("mkdist with vue-tsc ~v2.0.21", () => {
 
     expect(await readFile(resolve(rootDir, "dist/star/index.d.ts"), "utf8"))
       .toMatchInlineSnapshot(`
-        "export * from "./other.js";
-        export type { Other } from "./other.js";
+        "export * from "./other.mjs";
+        export type { Other } from "./other.mjs";
         "
       `);
     expect(
@@ -857,12 +1019,12 @@ describe("mkdist with vue-tsc ~v2.0.21", () => {
     expect(
       await readFile(resolve(rootDir, "dist/components/index.d.ts"), "utf8"),
     ).toMatchInlineSnapshot(`
-      "export * as jsx from "./jsx.jsx.js";
-      export * as tsx from "./tsx.tsx.js";
-      export * as blank from "./blank.vue.js";
-      export * as scriptSetupTS from "./script-setup-ts.vue.js";
-      export * as scriptMultiBlock from "./script-multi-block.vue.js";
-      export * as ts from "./ts.vue.js";
+      "export * as jsx from "./jsx.jsx.mjs";
+      export * as tsx from "./tsx.tsx.mjs";
+      export * as blank from "./blank.vue.mjs";
+      export * as scriptSetupTS from "./script-setup-ts.vue.mjs";
+      export * as scriptMultiBlock from "./script-multi-block.vue.mjs";
+      export * as ts from "./ts.vue.mjs";
       "
     `);