diff --git a/.changeset/query-key-fn.md b/.changeset/query-key-fn.md
new file mode 100644
index 000000000..4f012e99b
--- /dev/null
+++ b/.changeset/query-key-fn.md
@@ -0,0 +1,10 @@
+---
+"openapi-react-query": minor
+---
+
+Add `queryKeyFn` option to `createClient` for per-client query key namespacing.
+
+When two `openapi-fetch` clients target different servers but share endpoint paths,
+TanStack Query deduplicates their requests because the default `[method, path, init]`
+key is identical. Passing a `queryKeyFn` lets callers namespace keys per client
+instance so each client maintains an independent cache.
diff --git a/packages/openapi-react-query/README.md b/packages/openapi-react-query/README.md
index 50a521c4b..57b848f96 100644
--- a/packages/openapi-react-query/README.md
+++ b/packages/openapi-react-query/README.md
@@ -60,6 +60,37 @@ const MyComponent = () => {
 
 > You can find more information about `createFetchClient` in the [openapi-fetch documentation](../openapi-fetch).
 
+## Options
+
+### `queryKeyFn`
+
+TanStack Query deduplicates cache entries by query key. By default, `openapi-react-query`
+builds keys as `[method, path, init]`. If you use two separate `openapi-fetch` clients
+that target different servers but share endpoint paths, their keys will collide — only
+one request will fire and both hooks will receive the same cached data.
+
+Pass a `queryKeyFn` to `createClient` to namespace keys per client instance:
+
+```ts
+import createFetchClient from "openapi-fetch";
+import createClient from "openapi-react-query";
+import type { paths } from "./my-openapi-3-schema";
+
+const appClient = createClient(
+  createFetchClient<paths>({ baseUrl: "https://app-api.example.com" }),
+);
+
+const pdmClient = createClient(
+  createFetchClient<paths>({ baseUrl: "https://pdm-api.example.com" }),
+  {
+    queryKeyFn: (method, path, init) => ["pdm", method, path, init],
+  },
+);
+```
+
+Each client now maintains its own cache namespace, so identical paths on different
+servers are fetched and stored independently.
+
 ## 📓 Docs
 
 [View Docs](https://openapi-ts.dev/openapi-react-query/)
diff --git a/packages/openapi-react-query/src/index.ts b/packages/openapi-react-query/src/index.ts
index fb9683164..24f4d0ee0 100644
--- a/packages/openapi-react-query/src/index.ts
+++ b/packages/openapi-react-query/src/index.ts
@@ -2,7 +2,6 @@ import {
   type DataTag,
   type InfiniteData,
   type QueryClient,
-  type QueryFunctionContext,
   type SkipToken,
   type UseInfiniteQueryOptions,
   type UseInfiniteQueryResult,
@@ -38,6 +37,12 @@ export type QueryKey<
   Init = MaybeOptionalInit<Paths[Path], Method>,
 > = Init extends undefined ? readonly [Method, Path] : readonly [Method, Path, Init];
 
+export type QueryKeyFn = (method: HttpMethod, path: string, init: unknown) => readonly unknown[];
+
+export interface CreateClientOptions {
+  queryKeyFn?: QueryKeyFn;
+}
+
 export type QueryOptionsFunction<Paths extends Record<string, Record<HttpMethod, {}>>, Media extends MediaType> = <
   Method extends HttpMethod,
   Path extends PathsWithMethod<Paths, Method>,
@@ -192,32 +197,31 @@ export type MethodResponse<
 // TODO: Add the ability to bring queryClient as argument
 export default function createClient<Paths extends {}, Media extends MediaType = MediaType>(
   client: FetchClient<Paths, Media>,
+  clientOptions?: CreateClientOptions,
 ): OpenapiQueryClient<Paths, Media> {
-  const queryFn = async <Method extends HttpMethod, Path extends PathsWithMethod<Paths, Method>>({
-    queryKey: [method, path, init],
-    signal,
-  }: QueryFunctionContext<QueryKey<Paths, Method, Path>>) => {
-    const mth = method.toUpperCase() as Uppercase<typeof method>;
-    const fn = client[mth] as ClientMethod<Paths, typeof method, Media>;
-    const { data, error, response } = await fn(path, { signal, ...(init as any) }); // TODO: find a way to avoid as any
-    if (error) {
-      throw error;
-    }
-    if (response.status === 204 || response.headers.get("Content-Length") === "0") {
-      return data ?? null;
-    }
+  const buildQueryKey: QueryKeyFn =
+    clientOptions?.queryKeyFn ??
+    ((method, path, init) => (init === undefined ? ([method, path] as const) : ([method, path, init] as const)));
 
-    return data;
-  };
-
-  const queryOptions: QueryOptionsFunction<Paths, Media> = (method, path, ...[init, options]) => ({
-    queryKey: (init === undefined ? ([method, path] as const) : ([method, path, init] as const)) as DataTag<
+  const queryOptions: QueryOptionsFunction<Paths, Media> = (method, path, ...[init, queryOpts]) => ({
+    queryKey: buildQueryKey(method, path as string, init) as DataTag<
       QueryKey<Paths, typeof method, typeof path>,
       any,
       any
     >,
-    queryFn,
-    ...options,
+    queryFn: async ({ signal }) => {
+      const mth = method.toUpperCase() as Uppercase<typeof method>;
+      const fn = client[mth] as ClientMethod<Paths, typeof method, Media>;
+      const { data, error, response } = await fn(path, { signal, ...(init as any) }); // TODO: find a way to avoid as any
+      if (error) {
+        throw error;
+      }
+      if (response.status === 204 || response.headers.get("Content-Length") === "0") {
+        return data ?? null;
+      }
+      return data;
+    },
+    ...queryOpts,
   });
 
   return {
@@ -232,7 +236,7 @@ export default function createClient<Paths extends {}, Media extends MediaType =
       return useInfiniteQuery(
         {
           queryKey,
-          queryFn: async ({ queryKey: [method, path, init], pageParam = 0, signal }) => {
+          queryFn: async ({ pageParam = 0, signal }) => {
             const mth = method.toUpperCase() as Uppercase<typeof method>;
             const fn = client[mth] as ClientMethod<Paths, typeof method, Media>;
             const mergedInit = {
diff --git a/packages/openapi-react-query/test/index.test.tsx b/packages/openapi-react-query/test/index.test.tsx
index 78715e643..969e8e3fa 100644
--- a/packages/openapi-react-query/test/index.test.tsx
+++ b/packages/openapi-react-query/test/index.test.tsx
@@ -286,6 +286,98 @@ describe("client", () => {
     });
   });
 
+  describe("queryKeyFn", () => {
+    it("default key is [method, path] when no init is provided", () => {
+      const fetchClient = createFetchClient<minimalGetPaths>({ baseUrl });
+      const client = createClient(fetchClient);
+
+      const { queryKey } = client.queryOptions("get", "/foo");
+      expect(queryKey).toEqual(["get", "/foo"]);
+    });
+
+    it("default key is [method, path, init] when init is provided", () => {
+      const fetchClient = createFetchClient<minimalGetPaths>({ baseUrl });
+      const client = createClient(fetchClient);
+
+      const { queryKey } = client.queryOptions("get", "/foo", {});
+      expect(queryKey).toEqual(["get", "/foo", {}]);
+    });
+
+    it("uses custom queryKeyFn when provided", () => {
+      const fetchClient = createFetchClient<minimalGetPaths>({ baseUrl });
+      const client = createClient(fetchClient, {
+        queryKeyFn: (method, path, init) => ["ns", method, path, init],
+      });
+
+      const { queryKey } = client.queryOptions("get", "/foo");
+      expect(queryKey).toEqual(["ns", "get", "/foo", undefined]);
+    });
+
+    it("custom queryKeyFn prevents deduplication across clients with different namespaces", async () => {
+      const response = ["one", "two", "three"];
+
+      const fetchClient = createFetchClient<paths>({ baseUrl });
+      const client1 = createClient(fetchClient, {
+        queryKeyFn: (method, path, init) => ["ns1", method, path, init],
+      });
+      const client2 = createClient(fetchClient, {
+        queryKeyFn: (method, path, init) => ["ns2", method, path, init],
+      });
+
+      useMockRequestHandler({
+        baseUrl,
+        method: "get",
+        path: "/string-array",
+        status: 200,
+        body: response,
+      });
+
+      const { result: result1 } = renderHook(() => client1.useQuery("get", "/string-array"), { wrapper });
+      const { result: result2 } = renderHook(() => client2.useQuery("get", "/string-array"), { wrapper });
+
+      await waitFor(() => {
+        expect(result1.current.isFetching).toBe(false);
+        expect(result2.current.isFetching).toBe(false);
+      });
+
+      // Both clients should have data resolved independently
+      expect(result1.current.data).toEqual(response);
+      expect(result2.current.data).toEqual(response);
+
+      // Two separate cache entries should exist — one per namespace
+      const cacheKeys = queryClient
+        .getQueryCache()
+        .getAll()
+        .map((q) => q.queryKey);
+      expect(cacheKeys.some((k) => k[0] === "ns1")).toBe(true);
+      expect(cacheKeys.some((k) => k[0] === "ns2")).toBe(true);
+    });
+
+    it("custom queryKeyFn receives data via useQuery", async () => {
+      const response = ["one", "two", "three"];
+
+      const fetchClient = createFetchClient<paths>({ baseUrl });
+      const client = createClient(fetchClient, {
+        queryKeyFn: (method, path, init) => ["custom", method, path, init],
+      });
+
+      useMockRequestHandler({
+        baseUrl,
+        method: "get",
+        path: "/string-array",
+        status: 200,
+        body: response,
+      });
+
+      const { result } = renderHook(() => client.useQuery("get", "/string-array"), { wrapper });
+
+      await waitFor(() => expect(result.current.isFetching).toBe(false));
+
+      expect(result.current.data).toEqual(response);
+      expect(result.current.error).toBeNull();
+    });
+  });
+
   describe("useQuery", () => {
     it("should resolve data properly and have error as null when successful request", async () => {
       const response = ["one", "two", "three"];