diff --git a/.changeset/humble-humans-sink.md b/.changeset/humble-humans-sink.md
new file mode 100644
index 000000000000..92302e191c51
--- /dev/null
+++ b/.changeset/humble-humans-sink.md
@@ -0,0 +1,5 @@
+---
+'@astrojs/node': patch
+---
+
+Fixes an issue where static headers weren't correctly applied when the website uses `base`.
diff --git a/packages/integrations/node/src/serve-static.ts b/packages/integrations/node/src/serve-static.ts
index 610c1f0e9fb9..917a24db5c6c 100644
--- a/packages/integrations/node/src/serve-static.ts
+++ b/packages/integrations/node/src/serve-static.ts
@@ -48,7 +48,13 @@ export function createStaticHandler(
 				});
 				const routeData = app.match(request, true);
 				if (routeData && routeData.prerender) {
-					const matchedRoute = headersMap.find((header) => header.pathname.includes(pathname));
+					// Headers are stored keyed by base-less route paths (e.g. "/one"), so we
+					// must strip config.base from the incoming URL before matching, just as
+					// we do for filesystem access above.
+					const baselessPathname = prependForwardSlash(app.removeBase(urlPath));
+					const matchedRoute = headersMap.find((header) =>
+						header.pathname.includes(baselessPathname),
+					);
 					if (matchedRoute) {
 						for (const header of matchedRoute.headers) {
 							res.setHeader(header.key, header.value);
diff --git a/packages/integrations/node/test/static-headers.test.js b/packages/integrations/node/test/static-headers.test.js
index 86c124200879..3dc3d98f4c37 100644
--- a/packages/integrations/node/test/static-headers.test.js
+++ b/packages/integrations/node/test/static-headers.test.js
@@ -36,11 +36,13 @@ describe('Static headers', () => {
 	before(async () => {
 		fixture = await loadFixture({
 			root: './fixtures/static-headers/',
+			outDir: './dist/root-base',
 			output: 'server',
 			adapter: nodejs({ mode: 'standalone', staticHeaders: true }),
 		});
 		await fixture.build();
 		const { startServer } = await fixture.loadAdapterEntryModule();
+		process.env.PORT = '4322';
 		const res = startServer();
 		server = res.server;
 		await waitServerListen(server.server);
@@ -69,3 +71,49 @@ describe('Static headers', () => {
 		);
 	});
 });
+
+describe('Static headers with non-root base', () => {
+	/** @type {import('./test-utils').Fixture} */
+	let fixture;
+	let server;
+
+	before(async () => {
+		fixture = await loadFixture({
+			root: './fixtures/static-headers/',
+			outDir: './dist/non-root-base',
+			base: '/docs',
+			output: 'server',
+			adapter: nodejs({ mode: 'standalone', staticHeaders: true }),
+		});
+		await fixture.build();
+		const { startServer } = await fixture.loadAdapterEntryModule();
+		process.env.PORT = '4323';
+		const res = startServer();
+		server = res.server;
+		await waitServerListen(server.server);
+	});
+
+	after(async () => {
+		await server.stop();
+	});
+
+	it('CSP headers are added to the index route under the base path', async () => {
+		const res = await fetch(`http://${server.host}:${server.port}/docs/`);
+		const csp = res.headers.get('Content-Security-Policy');
+		assert.ok(csp, 'Content-Security-Policy header must be present for the index route');
+		assert.ok(
+			csp.includes('script-src'),
+			'should contain script-src directive due to server island',
+		);
+	});
+
+	it('CSP headers are added to a dynamic route under the base path', async () => {
+		const res = await fetch(`http://${server.host}:${server.port}/docs/one`);
+		const csp = res.headers.get('Content-Security-Policy');
+		assert.ok(csp, 'Content-Security-Policy header must be present for dynamic routes');
+		assert.ok(
+			csp.includes('script-src'),
+			'should contain script-src directive due to server island',
+		);
+	});
+});