diff --git a/packages/api/src/builder/routes.ts b/packages/api/src/builder/routes.ts
index 991c7ecbb55b..f1612aca17bb 100644
--- a/packages/api/src/builder/routes.ts
+++ b/packages/api/src/builder/routes.ts
@@ -1,8 +1,8 @@
 import {fromHexString, toHexString} from "@chainsafe/ssz";
-import {ssz, allForks, bellatrix, Slot, Root, BLSPubkey, StateId} from "@lodestar/types";
+import {ssz, allForks, bellatrix, Slot, Root, BLSPubkey, ValidatorIndex, WithdrawalIndex} from "@lodestar/types";
 import {ForkName, isForkExecution, isForkBlobs} from "@lodestar/params";
 import {ChainForkConfig} from "@lodestar/config";
-
+import {UintNum64} from "@lodestar/types/src/primitive/types.js";
 import {
   ReturnTypes,
   RoutesData,
@@ -13,11 +13,21 @@ import {
   ReqEmpty,
   ArrayOf,
   WithVersion,
+  jsonType,
 } from "../utils/index.js";
 // See /packages/api/src/routes/index.ts for reasoning and instructions to add new routes
 import {getReqSerializers as getBeaconReqSerializers} from "../beacon/routes/beacon/block.js";
 import {HttpStatusCode} from "../utils/client/httpStatusCode.js";
 import {ApiClientResponse} from "../interfaces.js";
+import {StateId, ExecutionOptimistic} from "../beacon/routes/beacon/state.js";
+
+export type Finalized = boolean;
+export type ExpectedWithdrawals = {
+  index: WithdrawalIndex;
+  validatorIndex: ValidatorIndex;
+  address: string;
+  amount: UintNum64;
+};
 
 export type Api = {
   status(): Promise<ApiClientResponse<{[HttpStatusCode.OK]: void}, HttpStatusCode.SERVICE_UNAVAILABLE>>;
@@ -46,10 +56,17 @@ export type Api = {
     >
   >;
   getExpectedWithdrawals(
-   stateId: StateId
+    state_id: StateId,
+    proposal_slot?: Slot
   ): Promise<
     ApiClientResponse<
-      {[HttpStatusCode.OK]: {execution_optimistic: Boolean, finalized: Boolean; data: allForks.SignedBuilderBid}},
+      {
+        [HttpStatusCode.OK]: {
+          executionOptimistic: ExecutionOptimistic;
+          finalized: Finalized;
+          data: ExpectedWithdrawals[];
+        };
+      },
       HttpStatusCode.NOT_FOUND | HttpStatusCode.BAD_REQUEST
     >
   >;
@@ -72,7 +89,7 @@ export type ReqTypes = {
   registerValidator: {body: unknown};
   getHeader: {params: {slot: Slot; parent_hash: string; pubkey: string}};
   submitBlindedBlock: {body: unknown};
-  getExpectedWithdrawals: {query: {proposal_slot: Slot}};
+  getExpectedWithdrawals: {params: {state_id: StateId}; query: {proposal_slot?: Slot}};
 };
 
 export function getReqSerializers(config: ChainForkConfig): ReqSerializers<Api, ReqTypes> {
@@ -89,6 +106,17 @@ export function getReqSerializers(config: ChainForkConfig): ReqSerializers<Api,
       },
     },
     submitBlindedBlock: getBeaconReqSerializers(config)["publishBlindedBlock"],
+    getExpectedWithdrawals: {
+      writeReq: (state_id, proposal_slot) => ({
+        params: {state_id},
+        query: {proposal_slot},
+      }),
+      parseReq: ({params, query}) => [params.state_id, query.proposal_slot ?? 0],
+      schema: {
+        params: {state_id: Schema.StringRequired},
+        query: {proposal_slot: Schema.Uint},
+      },
+    },
   };
 }
 
@@ -105,5 +133,6 @@ export function getReturnTypes(): ReturnTypes<Api> {
             ? ssz.allForksExecution[fork].ExecutionPayload
             : ssz.bellatrix.ExecutionPayload
     ),
+    getExpectedWithdrawals: jsonType("snake"),
   };
 }
diff --git a/packages/api/test/unit/builder/testData.ts b/packages/api/test/unit/builder/testData.ts
index e198e6971905..cb949dda8d53 100644
--- a/packages/api/test/unit/builder/testData.ts
+++ b/packages/api/test/unit/builder/testData.ts
@@ -26,4 +26,19 @@ export const testData: GenericServerTestCases<Api> = {
     args: [ssz.deneb.SignedBlindedBeaconBlock.defaultValue()],
     res: {version: ForkName.bellatrix, data: ssz.bellatrix.ExecutionPayload.defaultValue()},
   },
+  getExpectedWithdrawals: {
+    args: ["head", 1],
+    res: {
+      executionOptimistic: false,
+      finalized: false,
+      data: [
+        {
+          index: 1,
+          validatorIndex: 1,
+          address: "0xAbcF8e0d4e9587369b2301D0790347320302cc09",
+          amount: 1,
+        },
+      ],
+    },
+  },
 };