diff --git a/.changeset/fluffy-cheetahs-remain.md b/.changeset/fluffy-cheetahs-remain.md
new file mode 100644
index 000000000000..bf4424eb6222
--- /dev/null
+++ b/.changeset/fluffy-cheetahs-remain.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+handle undefined body on endpoint output
diff --git a/packages/kit/src/runtime/server/endpoint.js b/packages/kit/src/runtime/server/endpoint.js
index 0467f418413b..c3349929da08 100644
--- a/packages/kit/src/runtime/server/endpoint.js
+++ b/packages/kit/src/runtime/server/endpoint.js
@@ -25,12 +25,11 @@ export default async function render_route(request, route) {
 		const params = route.params(match);
 
 		const response = await handler({ ...request, params });
+		const preface = `Invalid response from route ${request.path}`;
 
 		if (response) {
 			if (typeof response !== 'object') {
-				return error(
-					`Invalid response from route ${request.path}: expected an object, got ${typeof response}`
-				);
+				return error(`${preface}: expected an object, got ${typeof response}`);
 			}
 
 			let { status = 200, body, headers = {} } = response;
@@ -41,13 +40,13 @@ export default async function render_route(request, route) {
 			// validation
 			if (type === 'application/octet-stream' && !(body instanceof Uint8Array)) {
 				return error(
-					`Invalid response from route ${request.path}: body must be an instance of Uint8Array if content type is application/octet-stream`
+					`${preface}: body must be an instance of Uint8Array if content type is application/octet-stream`
 				);
 			}
 
 			if (body instanceof Uint8Array && type !== 'application/octet-stream') {
 				return error(
-					`Invalid response from route ${request.path}: Uint8Array body must be accompanied by content-type: application/octet-stream header`
+					`${preface}: Uint8Array body must be accompanied by content-type: application/octet-stream header`
 				);
 			}
 
@@ -55,11 +54,11 @@ export default async function render_route(request, route) {
 			let normalized_body;
 
 			if (
-				typeof body === 'object' &&
-				(!type || type === 'application/json' || type === 'application/json; charset=utf-8')
+				(typeof body === 'object' || typeof body === 'undefined') &&
+				(!type || type.startsWith('application/json'))
 			) {
 				headers = { ...headers, 'content-type': 'application/json; charset=utf-8' };
-				normalized_body = JSON.stringify(body);
+				normalized_body = JSON.stringify(body || {});
 			} else {
 				normalized_body = /** @type {import('types/hooks').StrictBody} */ (body);
 			}
diff --git a/packages/kit/test/apps/basics/src/routes/endpoint-output/_tests.js b/packages/kit/test/apps/basics/src/routes/endpoint-output/_tests.js
new file mode 100644
index 000000000000..a65e96fe43b8
--- /dev/null
+++ b/packages/kit/test/apps/basics/src/routes/endpoint-output/_tests.js
@@ -0,0 +1,39 @@
+import * as assert from 'uvu/assert';
+
+/** @type {import('test').TestMaker} */
+export default function (test) {
+	test('not ok on void endpoint', null, async ({ fetch }) => {
+		const res = await fetch('/endpoint-output/empty', { method: 'DELETE' });
+		assert.equal(res.ok, false);
+	});
+	test('200 status on empty endpoint', null, async ({ fetch }) => {
+		const res = await fetch('/endpoint-output/empty');
+		assert.equal(res.status, 200);
+		assert.equal(await res.json(), {});
+	});
+
+	test('set-cookie without body', null, async ({ fetch }) => {
+		const res = await fetch('/endpoint-output/headers');
+		assert.equal(res.status, 200);
+		assert.equal(res.headers.has('set-cookie'), true);
+	});
+
+	test('200 status by default', null, async ({ fetch }) => {
+		const res = await fetch('/endpoint-output/body');
+		assert.equal(res.status, 200);
+		assert.equal(await res.text(), '{}');
+	});
+
+	test('does not throw on blob method', null, async ({ fetch }) => {
+		const res = await fetch('/endpoint-output/empty');
+		assert.type(await res.blob(), 'object');
+	});
+	test('does not throw on arrayBuffer method', null, async ({ fetch }) => {
+		const res = await fetch('/endpoint-output/empty');
+		assert.type(await res.arrayBuffer(), 'object');
+	});
+	test('does not throw on buffer method', null, async ({ fetch }) => {
+		const res = await fetch('/endpoint-output/empty');
+		assert.type(await res.buffer(), 'object');
+	});
+}
diff --git a/packages/kit/test/apps/basics/src/routes/endpoint-output/body.js b/packages/kit/test/apps/basics/src/routes/endpoint-output/body.js
new file mode 100644
index 000000000000..6cafc71b6f6f
--- /dev/null
+++ b/packages/kit/test/apps/basics/src/routes/endpoint-output/body.js
@@ -0,0 +1,4 @@
+/** @type {import('@sveltejs/kit').RequestHandler} */
+export function get() {
+	return { body: {} };
+}
diff --git a/packages/kit/test/apps/basics/src/routes/endpoint-output/empty.js b/packages/kit/test/apps/basics/src/routes/endpoint-output/empty.js
new file mode 100644
index 000000000000..78ba9f6fb252
--- /dev/null
+++ b/packages/kit/test/apps/basics/src/routes/endpoint-output/empty.js
@@ -0,0 +1,7 @@
+/** @type {import('@sveltejs/kit').RequestHandler} */
+export function get() {
+	return {};
+}
+
+/** @type {import('@sveltejs/kit').RequestHandler} */
+export function del() {}
diff --git a/packages/kit/test/apps/basics/src/routes/endpoint-output/headers.js b/packages/kit/test/apps/basics/src/routes/endpoint-output/headers.js
new file mode 100644
index 000000000000..481f0f882e4d
--- /dev/null
+++ b/packages/kit/test/apps/basics/src/routes/endpoint-output/headers.js
@@ -0,0 +1,8 @@
+/** @type {import('@sveltejs/kit').RequestHandler} */
+export function get() {
+	return {
+		headers: {
+			'Set-Cookie': 'foo=bar'
+		}
+	};
+}