diff --git a/.changeset/odd-ways-dress.md b/.changeset/odd-ways-dress.md
new file mode 100644
index 0000000000..7d8c8630f6
--- /dev/null
+++ b/.changeset/odd-ways-dress.md
@@ -0,0 +1,5 @@
+---
+"@effect/platform": patch
+---
+
+Add `HttpRouter.concatAll`.
diff --git a/.changeset/ten-ties-guess.md b/.changeset/ten-ties-guess.md
new file mode 100644
index 0000000000..dbe5659c7e
--- /dev/null
+++ b/.changeset/ten-ties-guess.md
@@ -0,0 +1,5 @@
+---
+"@effect/platform": patch
+---
+
+Fix `HttpRouter.concat` - add mounts from both routers.
diff --git a/packages/platform-node/test/HttpServer.test.ts b/packages/platform-node/test/HttpServer.test.ts
index ddd3840b85..610bdaeb50 100644
--- a/packages/platform-node/test/HttpServer.test.ts
+++ b/packages/platform-node/test/HttpServer.test.ts
@@ -701,4 +701,44 @@ describe("HttpServer", () => {
       const res = yield* HttpClientRequest.get("/").pipe(client)
       assert.deepStrictEqual(res.status, 500)
     }).pipe(Effect.provide(NodeHttpServer.layerTest)))
+
+  const routerA = HttpRouter.empty.pipe(
+    HttpRouter.get("/a", HttpServerResponse.text("a")),
+    HttpRouter.mountApp("/ma", HttpServerResponse.text("ma"))
+  )
+
+  const routerB = HttpRouter.empty.pipe(
+    HttpRouter.get("/b", HttpServerResponse.text("b")),
+    HttpRouter.mountApp("/mb", HttpServerResponse.text("mb"))
+  )
+
+  it.scoped("concat", () =>
+    Effect.gen(function*() {
+      yield* HttpRouter.concat(routerA, routerB).pipe(HttpServer.serveEffect())
+      const [responseA, responseMountA, responseB, responseMountB] = yield* Effect.all([
+        HttpClientRequest.get("/a"),
+        HttpClientRequest.get("/ma"),
+        HttpClientRequest.get("/b"),
+        HttpClientRequest.get("/mb")
+      ])
+      expect(yield* responseA.text).toEqual("a")
+      expect(yield* responseMountA.text).toEqual("ma")
+      expect(yield* responseB.text).toEqual("b")
+      expect(yield* responseMountB.text).toEqual("mb")
+    }).pipe(Effect.provide(NodeHttpServer.layerTest)))
+
+  it.scoped("concatAll", () =>
+    Effect.gen(function*() {
+      yield* HttpRouter.concatAll(routerA, routerB).pipe(HttpServer.serveEffect())
+      const [responseA, responseMountA, responseB, responseMountB] = yield* Effect.all([
+        HttpClientRequest.get("/a"),
+        HttpClientRequest.get("/ma"),
+        HttpClientRequest.get("/b"),
+        HttpClientRequest.get("/mb")
+      ])
+      expect(yield* responseA.text).toEqual("a")
+      expect(yield* responseMountA.text).toEqual("ma")
+      expect(yield* responseB.text).toEqual("b")
+      expect(yield* responseMountB.text).toEqual("mb")
+    }).pipe(Effect.provide(NodeHttpServer.layerTest)))
 })
diff --git a/packages/platform/dtslint/HttpRouter.ts b/packages/platform/dtslint/HttpRouter.ts
new file mode 100644
index 0000000000..baa7937497
--- /dev/null
+++ b/packages/platform/dtslint/HttpRouter.ts
@@ -0,0 +1,8 @@
+import * as HttpRouter from "@effect/platform/HttpRouter"
+
+declare const router1: HttpRouter.HttpRouter<"E1", "R1">
+declare const router2: HttpRouter.HttpRouter<"E2", "R2">
+declare const router3: HttpRouter.HttpRouter<"E3", "R3">
+
+// $ExpectType HttpRouter<"E1" | "E2" | "E3", "R1" | "R2" | "R3">
+HttpRouter.concatAll(router1, router2, router3)
diff --git a/packages/platform/dtslint/tsconfig.json b/packages/platform/dtslint/tsconfig.json
new file mode 100644
index 0000000000..6b2c70900f
--- /dev/null
+++ b/packages/platform/dtslint/tsconfig.json
@@ -0,0 +1,9 @@
+{
+  "extends": "../../../tsconfig.base.json",
+  "include": ["."],
+  "compilerOptions": {
+    "incremental": false,
+    "composite": false,
+    "noUnusedLocals": false
+  }
+}
diff --git a/packages/platform/package.json b/packages/platform/package.json
index cdacdc7400..a0af958edc 100644
--- a/packages/platform/package.json
+++ b/packages/platform/package.json
@@ -34,6 +34,7 @@
     "build-esm": "tsc -b tsconfig.build.json",
     "build-cjs": "babel build/esm --plugins @babel/transform-export-namespace-from --plugins @babel/transform-modules-commonjs --out-dir build/cjs --source-maps",
     "build-annotate": "babel build/esm --plugins annotate-pure-calls --out-dir build/esm --source-maps",
+    "dtslint": "dtslint dtslint",
     "check": "tsc -b tsconfig.json",
     "test": "vitest",
     "coverage": "vitest --coverage"
diff --git a/packages/platform/src/HttpRouter.ts b/packages/platform/src/HttpRouter.ts
index fbb4ac44f6..a9c5447569 100644
--- a/packages/platform/src/HttpRouter.ts
+++ b/packages/platform/src/HttpRouter.ts
@@ -379,6 +379,14 @@ export const concat: {
   >
 } = internal.concat
 
+/**
+ * @since 1.0.0
+ * @category combinators
+ */
+export const concatAll: <Routers extends ReadonlyArray<HttpRouter<unknown, unknown>>>(
+  ...routers: Routers
+) => [Routers[number]] extends [HttpRouter<infer E, infer R>] ? HttpRouter<E, R> : never = internal.concatAll
+
 /**
  * @since 1.0.0
  * @category routing
diff --git a/packages/platform/src/internal/httpRouter.ts b/packages/platform/src/internal/httpRouter.ts
index 671cad187d..973dae2ca1 100644
--- a/packages/platform/src/internal/httpRouter.ts
+++ b/packages/platform/src/internal/httpRouter.ts
@@ -351,7 +351,25 @@ export const concat = dual<
     that: Router.HttpRouter<E1, R1>
   ) => <E, R>(self: Router.HttpRouter<E, R>) => Router.HttpRouter<E | E1, R | R1>,
   <E, R, E1, R1>(self: Router.HttpRouter<E, R>, that: Router.HttpRouter<E1, R1>) => Router.HttpRouter<E | E1, R | R1>
->(2, (self, that) => new RouterImpl(Chunk.appendAll(self.routes, that.routes) as any, self.mounts))
+>(2, (self, that) => concatAll(self, that))
+
+/** @internal */
+export const concatAll = <Routers extends ReadonlyArray<Router.HttpRouter<E, R>>, E, R>(
+  ...routers: Routers
+) =>
+  new RouterImpl(
+    routers.reduce((cur, acc) => Chunk.appendAll(cur, acc.routes), Chunk.empty<Router.Route<E, R>>()),
+    routers.reduce(
+      (cur, acc) => Chunk.appendAll(cur, acc.mounts),
+      Chunk.empty<
+        readonly [
+          prefix: string,
+          httpApp: App.Default<E, R>,
+          options?: { readonly includePrefix?: boolean | undefined } | undefined
+        ]
+      >()
+    )
+  ) as any
 
 const removeTrailingSlash = (
   path: Router.PathInput