diff --git a/packages/api/src/builder/routes.ts b/packages/api/src/builder/routes.ts
index 018110e5ede..a203a93b8af 100644
--- a/packages/api/src/builder/routes.ts
+++ b/packages/api/src/builder/routes.ts
@@ -78,9 +78,6 @@ export type Endpoints = {
   >;
 };
 
-// NOTE: Builder API does not support SSZ as per spec, need to keep routes as JSON-only for now
-// See https://github.com/ethereum/builder-specs/issues/53 for more details
-
 export function getDefinitions(config: ChainForkConfig): RouteDefinitions<Endpoints> {
   return {
     status: {
@@ -125,7 +122,7 @@ export function getDefinitions(config: ChainForkConfig): RouteDefinitions<Endpoi
     submitBlindedBlock: {
       url: "/eth/v1/builder/blinded_blocks",
       method: "POST",
-      req: JsonOnlyReq({
+      req: {
         writeReqJson: ({signedBlindedBlock}) => {
           const fork = config.getForkName(signedBlindedBlock.message.slot);
           return {
@@ -141,11 +138,26 @@ export function getDefinitions(config: ChainForkConfig): RouteDefinitions<Endpoi
             signedBlindedBlock: getExecutionForkTypes(fork).SignedBlindedBeaconBlock.fromJson(body),
           };
         },
+        writeReqSsz: ({signedBlindedBlock}) => {
+          const fork = config.getForkName(signedBlindedBlock.message.slot);
+          return {
+            body: getExecutionForkTypes(fork).SignedBlindedBeaconBlock.serialize(signedBlindedBlock),
+            headers: {
+              [MetaHeader.Version]: fork,
+            },
+          };
+        },
+        parseReqSsz: ({body, headers}) => {
+          const fork = toForkName(fromHeaders(headers, MetaHeader.Version));
+          return {
+            signedBlindedBlock: getExecutionForkTypes(fork).SignedBlindedBeaconBlock.deserialize(body),
+          };
+        },
         schema: {
           body: Schema.Object,
           headers: {[MetaHeader.Version]: Schema.String},
         },
-      }),
+      },
       resp: {
         data: WithVersion<ExecutionPayload | ExecutionPayloadAndBlobsBundle, VersionMeta>((fork: ForkName) => {
           return isForkBlobs(fork)
diff --git a/packages/beacon-node/src/execution/builder/http.ts b/packages/beacon-node/src/execution/builder/http.ts
index 87920e833f5..814fee72cd8 100644
--- a/packages/beacon-node/src/execution/builder/http.ts
+++ b/packages/beacon-node/src/execution/builder/http.ts
@@ -18,6 +18,7 @@ import {SLOTS_PER_EPOCH, ForkExecution} from "@lodestar/params";
 import {toPrintableUrl} from "@lodestar/utils";
 import {Metrics} from "../../metrics/metrics.js";
 import {IExecutionBuilder} from "./interface.js";
+import {WireFormat} from "@lodestar/api";
 
 export type ExecutionBuilderHttpOpts = {
   enabled: boolean;
@@ -53,6 +54,13 @@ export class ExecutionBuilderHttp implements IExecutionBuilder {
   faultInspectionWindow: number;
   allowedFaults: number;
 
+  /**
+   * Determine if SSZ is supported by requesting an SSZ encoded response in the `getHeader` request.
+   * If the builder responds with a SSZ serialized `SignedBuilderBid` it indicates support for submitting
+   * the `SignedBlindedBeaconBlock` as SSZ serialized bytes instead of JSON via `submitBlindedBlock`.
+   */
+  private sszSupported = false;
+
   constructor(
     opts: ExecutionBuilderHttpOpts,
     config: ChainForkConfig,
@@ -123,14 +131,18 @@ export class ExecutionBuilderHttp implements IExecutionBuilder {
     blobKzgCommitments?: deneb.BlobKzgCommitments;
     executionRequests?: electra.ExecutionRequests;
   }> {
-    const signedBuilderBid = (
-      await this.api.getHeader({slot, parentHash, proposerPubkey}, {timeoutMs: BUILDER_PROPOSAL_DELAY_TOLERANCE})
-    ).value();
+    const res = await this.api.getHeader(
+      {slot, parentHash, proposerPubkey},
+      {timeoutMs: BUILDER_PROPOSAL_DELAY_TOLERANCE}
+    );
+    const signedBuilderBid = res.value();
 
     if (!signedBuilderBid) {
       throw Error("No bid received");
     }
 
+    this.sszSupported = res.wireFormat() === WireFormat.ssz;
+
     const {header, value: executionPayloadValue} = signedBuilderBid.message;
     const {blobKzgCommitments} = signedBuilderBid.message as deneb.BuilderBid;
     const {executionRequests} = signedBuilderBid.message as electra.BuilderBid;
@@ -138,9 +150,12 @@ export class ExecutionBuilderHttp implements IExecutionBuilder {
   }
 
   async submitBlindedBlock(signedBlindedBlock: SignedBlindedBeaconBlock): Promise<SignedBeaconBlockOrContents> {
-    const data = (await this.api.submitBlindedBlock({signedBlindedBlock}, {retries: 2})).value();
+    const res = await this.api.submitBlindedBlock(
+      {signedBlindedBlock},
+      {retries: 2, requestWireFormat: this.sszSupported ? WireFormat.ssz : WireFormat.json}
+    );
 
-    const {executionPayload, blobsBundle} = parseExecutionPayloadAndBlobsBundle(data);
+    const {executionPayload, blobsBundle} = parseExecutionPayloadAndBlobsBundle(res.value());
 
     // for the sake of timely proposals we can skip matching the payload with payloadHeader
     // if the roots (transactions, withdrawals) don't match, this will likely lead to a block with