diff --git a/.changeset/dry-brooms-care.md b/.changeset/dry-brooms-care.md
new file mode 100644
index 000000000..8318eba39
--- /dev/null
+++ b/.changeset/dry-brooms-care.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fix dynamic routes for sites with subpath
diff --git a/packages/astro/src/core/dev/index.ts b/packages/astro/src/core/dev/index.ts
index a424c43f8..6fb0e3e3e 100644
--- a/packages/astro/src/core/dev/index.ts
+++ b/packages/astro/src/core/dev/index.ts
@@ -319,7 +319,7 @@ export class AstroDevServer {
 				logging: this.logging,
 				mode: 'development',
 				origin: this.origin,
-				pathname,
+				pathname: routePathname,
 				route,
 				routeCache: this.routeCache,
 				viteServer: this.viteServer,
diff --git a/packages/astro/test/dev-routing.test.js b/packages/astro/test/dev-routing.test.js
index 2ed506335..1f5647935 100644
--- a/packages/astro/test/dev-routing.test.js
+++ b/packages/astro/test/dev-routing.test.js
@@ -32,6 +32,16 @@ describe('Development Routing', () => {
 			const response = await fixture.fetch('/another');
 			expect(response.status).to.equal(200);
 		});
+
+		it('200 when loading dynamic route', async () => {
+			const response = await fixture.fetch('/1');
+			expect(response.status).to.equal(200);
+		});
+
+		it('500 when loading invalid dynamic route', async () => {
+			const response = await fixture.fetch('/2');
+			expect(response.status).to.equal(500);
+		});
 	});
 
 	describe('No subpath used', () => {
@@ -58,6 +68,16 @@ describe('Development Routing', () => {
 			const response = await fixture.fetch('/another');
 			expect(response.status).to.equal(200);
 		});
+
+		it('200 when loading dynamic route', async () => {
+			const response = await fixture.fetch('/1');
+			expect(response.status).to.equal(200);
+		});
+
+		it('500 when loading invalid dynamic route', async () => {
+			const response = await fixture.fetch('/2');
+			expect(response.status).to.equal(500);
+		});
 	});
 
 	describe('Subpath with trailing slash', () => {
@@ -94,6 +114,16 @@ describe('Development Routing', () => {
 			const response = await fixture.fetch('/blog/another/');
 			expect(response.status).to.equal(200);
 		});
+
+		it('200 when loading dynamic route', async () => {
+			const response = await fixture.fetch('/blog/1/');
+			expect(response.status).to.equal(200);
+		});
+
+		it('500 when loading invalid dynamic route', async () => {
+			const response = await fixture.fetch('/blog/2/');
+			expect(response.status).to.equal(500);
+		});
 	});
 
 	describe('Subpath without trailing slash', () => {
@@ -130,5 +160,15 @@ describe('Development Routing', () => {
 			const response = await fixture.fetch('/blog/another/');
 			expect(response.status).to.equal(200);
 		});
+
+		it('200 when loading dynamic route', async () => {
+			const response = await fixture.fetch('/blog/1/');
+			expect(response.status).to.equal(200);
+		});
+
+		it('500 when loading invalid dynamic route', async () => {
+			const response = await fixture.fetch('/blog/2/');
+			expect(response.status).to.equal(500);
+		});
 	});
 });
diff --git a/packages/astro/test/fixtures/with-subpath-no-trailing-slash/src/pages/[id].astro b/packages/astro/test/fixtures/with-subpath-no-trailing-slash/src/pages/[id].astro
new file mode 100644
index 000000000..b5dbc4307
--- /dev/null
+++ b/packages/astro/test/fixtures/with-subpath-no-trailing-slash/src/pages/[id].astro
@@ -0,0 +1,6 @@
+---
+export function getStaticPaths() {
+  return [{ params: { id: '1' } }];
+}
+---
+<h1>Post #1</h1>
diff --git a/packages/astro/test/fixtures/with-subpath-trailing-slash/src/pages/[id].astro b/packages/astro/test/fixtures/with-subpath-trailing-slash/src/pages/[id].astro
new file mode 100644
index 000000000..b5dbc4307
--- /dev/null
+++ b/packages/astro/test/fixtures/with-subpath-trailing-slash/src/pages/[id].astro
@@ -0,0 +1,6 @@
+---
+export function getStaticPaths() {
+  return [{ params: { id: '1' } }];
+}
+---
+<h1>Post #1</h1>
diff --git a/packages/astro/test/fixtures/without-site-config/src/pages/[id].astro b/packages/astro/test/fixtures/without-site-config/src/pages/[id].astro
new file mode 100644
index 000000000..b5dbc4307
--- /dev/null
+++ b/packages/astro/test/fixtures/without-site-config/src/pages/[id].astro
@@ -0,0 +1,6 @@
+---
+export function getStaticPaths() {
+  return [{ params: { id: '1' } }];
+}
+---
+<h1>Post #1</h1>
diff --git a/packages/astro/test/fixtures/without-subpath/src/pages/[id].astro b/packages/astro/test/fixtures/without-subpath/src/pages/[id].astro
new file mode 100644
index 000000000..b5dbc4307
--- /dev/null
+++ b/packages/astro/test/fixtures/without-subpath/src/pages/[id].astro
@@ -0,0 +1,6 @@
+---
+export function getStaticPaths() {
+  return [{ params: { id: '1' } }];
+}
+---
+<h1>Post #1</h1>