diff --git a/.changeset/clear-items-send.md b/.changeset/clear-items-send.md
new file mode 100644
index 00000000000..4d2792ad571
--- /dev/null
+++ b/.changeset/clear-items-send.md
@@ -0,0 +1,5 @@
+---
+"@effect/platform": patch
+---
+
+`HttpRouter.mountApp` prefix matching fixed
diff --git a/packages/platform-node/test/HttpServer.test.ts b/packages/platform-node/test/HttpServer.test.ts
index 5ae3117b219..59801f77d51 100644
--- a/packages/platform-node/test/HttpServer.test.ts
+++ b/packages/platform-node/test/HttpServer.test.ts
@@ -190,6 +190,14 @@ describe("HttpServer", () => {
       expect(todo).toEqual("/1")
       const root = yield* client.get("/child").pipe(Effect.flatMap((_) => _.text))
       expect(root).toEqual("/")
+      const rootSearch = yield* client.get("/child?foo=bar").pipe(Effect.flatMap((_) => _.text))
+      expect(rootSearch).toEqual("?foo=bar")
+      const rootSlash = yield* client.get("/child/").pipe(Effect.flatMap((_) => _.text))
+      expect(rootSlash).toEqual("/")
+      const invalid = yield* client.get("/child1/", {
+        urlParams: { foo: "bar" }
+      }).pipe(Effect.map((_) => _.status))
+      expect(invalid).toEqual(404)
     }).pipe(Effect.provide(NodeHttpServer.layerTest)))
 
   it.scoped("mountApp/includePrefix", () =>
diff --git a/packages/platform/src/internal/httpRouter.ts b/packages/platform/src/internal/httpRouter.ts
index e51148eddca..a8ba4bd281b 100644
--- a/packages/platform/src/internal/httpRouter.ts
+++ b/packages/platform/src/internal/httpRouter.ts
@@ -243,9 +243,12 @@ const toHttpApp = <E, R>(
     const context = Context.unsafeMake(new Map(fiber.getFiberRef(FiberRef.currentContext).unsafeMap))
     const request = Context.unsafeGet(context, ServerRequest.HttpServerRequest)
     if (mountsLen > 0) {
+      const searchIndex = request.url.indexOf("?")
+      const pathname = searchIndex === -1 ? request.url : request.url.slice(0, searchIndex)
+
       for (let i = 0; i < mountsLen; i++) {
         const [path, routeContext, options] = mounts[i]
-        if (request.url.startsWith(path)) {
+        if (pathname === path || pathname.startsWith(path + "/")) {
           context.unsafeMap.set(RouteContext.key, routeContext)
           if (options?.includePrefix !== true) {
             context.unsafeMap.set(ServerRequest.HttpServerRequest.key, sliceRequestUrl(request, path))