diff --git a/src/__tests__/api/master/sendMany.test.ts b/src/__tests__/api/master/sendMany.test.ts
index 0218baf..d599fa3 100644
--- a/src/__tests__/api/master/sendMany.test.ts
+++ b/src/__tests__/api/master/sendMany.test.ts
@@ -298,6 +298,10 @@ describe('POST /api/v1/:coin/advancedwallet/:walletId/sendMany', () => {
       response.body.should.have.property('txid', 'test-tx-id');
       response.body.should.have.property('tx', 'signed-transaction');
 
+      // Verify that type defaults to 'transfer' for TSS wallets when not provided
+      const sendManyArgs = sendManyStub.firstCall.args[0] as Record<string, unknown>;
+      sendManyArgs.should.have.property('type', 'transfer');
+
       walletGetNock.done();
       keychainGetNock.done();
       sinon.assert.calledOnce(sendManyStub);
diff --git a/src/masterBitgoExpress/handlers/handleSendMany.ts b/src/masterBitgoExpress/handlers/handleSendMany.ts
index e5fdaa5..9253bea 100644
--- a/src/masterBitgoExpress/handlers/handleSendMany.ts
+++ b/src/masterBitgoExpress/handlers/handleSendMany.ts
@@ -125,6 +125,10 @@ export async function handleSendMany(req: MasterApiSpecRouteRequest<'v1.wallet.s
       if (signingKeychain.source === 'backup') {
         throw new BadRequestError('Backup MPC signing not supported for sendMany');
       }
+      // TSS wallets require type to be set; default to 'transfer' if not provided
+      if (!params.type) {
+        params.type = 'transfer';
+      }
       const mpcSendParams = await createMPCSendParamsWithCustomSigningFns(
         req,
         awmClient,
diff --git a/src/masterBitgoExpress/routers/sendManyRoute.ts b/src/masterBitgoExpress/routers/sendManyRoute.ts
index 77bda70..608acdf 100644
--- a/src/masterBitgoExpress/routers/sendManyRoute.ts
+++ b/src/masterBitgoExpress/routers/sendManyRoute.ts
@@ -8,7 +8,7 @@ export const SendManyRequest = {
    */
   source: t.union([t.literal('user'), t.literal('backup')]),
   /**
-   * Required for transactions from MPC wallets.
+   * Required for transactions from MPC wallets. Defaults to 'transfer' for TSS wallets if not provided.
    */
   type: t.union([
     t.undefined,