diff --git a/modules/sdk-coin-hbar/src/lib/accountUpdateBuilder.ts b/modules/sdk-coin-hbar/src/lib/accountUpdateBuilder.ts
index 7f45709277..4a8393313f 100644
--- a/modules/sdk-coin-hbar/src/lib/accountUpdateBuilder.ts
+++ b/modules/sdk-coin-hbar/src/lib/accountUpdateBuilder.ts
@@ -11,6 +11,7 @@ export class AccountUpdateBuilder extends TransactionBuilder {
   private readonly _txBodyData: proto.CryptoUpdateTransactionBody;
   private _accountId: string;
   private _stakedNodeId?: Long;
+  private _stakedAccountId?: string;
   private _declineStakingReward?: boolean;
 
   constructor(_coinConfig: Readonly<CoinConfig>) {
@@ -30,6 +31,9 @@ export class AccountUpdateBuilder extends TransactionBuilder {
       if (updateBody.stakedNodeId != null) {
         this._stakedNodeId = Long.fromValue(updateBody.stakedNodeId);
       }
+      if (updateBody.stakedAccountId) {
+        this._stakedAccountId = stringifyAccountId(updateBody.stakedAccountId);
+      }
       if (updateBody.declineReward != null) {
         const raw = updateBody.declineReward;
         this._declineStakingReward = typeof raw === 'boolean' ? raw : (raw as { value: boolean }).value;
@@ -51,6 +55,9 @@ export class AccountUpdateBuilder extends TransactionBuilder {
     if (this._stakedNodeId !== undefined) {
       this._txBodyData.stakedNodeId = this._stakedNodeId;
     }
+    if (this._stakedAccountId !== undefined) {
+      this._txBodyData.stakedAccountId = buildHederaAccountID(this._stakedAccountId);
+    }
     if (this._declineStakingReward !== undefined) {
       this._txBodyData.declineReward = { value: this._declineStakingReward };
     }
@@ -60,8 +67,11 @@ export class AccountUpdateBuilder extends TransactionBuilder {
 
   /** @inheritdoc */
   validateMandatoryFields(): void {
-    if (this._stakedNodeId === undefined) {
-      throw new BuildTransactionError('Invalid transaction: missing stakedNodeId');
+    if (this._stakedNodeId === undefined && this._stakedAccountId === undefined) {
+      throw new BuildTransactionError('Invalid transaction: missing stakedNodeId or stakedAccountId');
+    }
+    if (this._stakedNodeId !== undefined && this._stakedAccountId !== undefined) {
+      throw new BuildTransactionError('Invalid transaction: cannot set both stakedNodeId and stakedAccountId');
     }
     super.validateMandatoryFields();
   }
@@ -94,6 +104,20 @@ export class AccountUpdateBuilder extends TransactionBuilder {
     return this;
   }
 
+  /**
+   * Set the staked account ID for indirect staking. Use "0.0.0" to unstake.
+   *
+   * @param {string} accountId - The account ID to stake to in format <shard>.<realm>.<account>, or "0.0.0" to clear
+   * @returns {AccountUpdateBuilder} - This builder
+   */
+  stakedAccountId(accountId: string): this {
+    if (!isValidAddress(accountId)) {
+      throw new BuildTransactionError('Invalid stakedAccountId: ' + accountId);
+    }
+    this._stakedAccountId = accountId;
+    return this;
+  }
+
   /**
    * Set whether to decline staking rewards.
    *
diff --git a/modules/sdk-coin-hbar/src/lib/iface.ts b/modules/sdk-coin-hbar/src/lib/iface.ts
index d1b08c9b4a..1bc1d2517f 100644
--- a/modules/sdk-coin-hbar/src/lib/iface.ts
+++ b/modules/sdk-coin-hbar/src/lib/iface.ts
@@ -61,6 +61,7 @@ export interface AccountUpdateInstruction {
   params: {
     accountId: string;
     stakedNodeId?: string;
+    stakedAccountId?: string;
     declineReward?: boolean;
   };
 }
diff --git a/modules/sdk-coin-hbar/src/lib/transaction.ts b/modules/sdk-coin-hbar/src/lib/transaction.ts
index 8f615e0960..c190c47de7 100644
--- a/modules/sdk-coin-hbar/src/lib/transaction.ts
+++ b/modules/sdk-coin-hbar/src/lib/transaction.ts
@@ -166,13 +166,21 @@ export class Transaction extends BaseTransaction {
    *
    * @returns {object} The account update parameters including stakedNodeId and declineReward
    */
-  private getAccountUpdateData(): { accountId: string; stakedNodeId?: string; declineReward?: boolean } {
+  private getAccountUpdateData(): {
+    accountId: string;
+    stakedNodeId?: string;
+    stakedAccountId?: string;
+    declineReward?: boolean;
+  } {
     const updateBody = this._txBody.cryptoUpdateAccount!;
     return {
       accountId: stringifyAccountId(updateBody.accountIDToUpdate!),
       ...(updateBody.stakedNodeId != null && {
         stakedNodeId: Long.fromValue(updateBody.stakedNodeId).toString(),
       }),
+      ...(updateBody.stakedAccountId && {
+        stakedAccountId: stringifyAccountId(updateBody.stakedAccountId),
+      }),
       ...(updateBody.declineReward != null && {
         declineReward:
           typeof updateBody.declineReward === 'boolean'
diff --git a/modules/sdk-coin-hbar/test/unit/transactionBuilder/accountUpdateBuilder.ts b/modules/sdk-coin-hbar/test/unit/transactionBuilder/accountUpdateBuilder.ts
index 89ec7ec6a1..e07e840531 100644
--- a/modules/sdk-coin-hbar/test/unit/transactionBuilder/accountUpdateBuilder.ts
+++ b/modules/sdk-coin-hbar/test/unit/transactionBuilder/accountUpdateBuilder.ts
@@ -130,6 +130,52 @@ describe('HBAR Account Update Builder', () => {
         const txJson = tx.toJson();
         txJson.instructionsData.params.accountId.should.deepEqual(testData.ACCOUNT_2.accountId);
       });
+
+      it('a stake-to-account transaction with stakedAccountId', async () => {
+        const txBuilder = factory.getAccountUpdateBuilder();
+        txBuilder.fee({ fee: testData.FEE });
+        txBuilder.source({ address: testData.ACCOUNT_1.accountId });
+        txBuilder.stakedAccountId(testData.ACCOUNT_2.accountId);
+        txBuilder.validDuration(1000000);
+        txBuilder.node({ nodeId: '0.0.2345' });
+        txBuilder.startTime('1596110493.372646570');
+        const tx = await txBuilder.build();
+        const txJson = tx.toJson();
+        txJson.instructionsData.params.stakedAccountId.should.deepEqual(testData.ACCOUNT_2.accountId);
+        txJson.instructionsData.params.accountId.should.deepEqual(testData.ACCOUNT_1.accountId);
+        should.not.exist(txJson.instructionsData.params.stakedNodeId);
+        tx.type.should.equal(TransactionType.AccountUpdate);
+      });
+
+      it('an unstake-from-account transaction with sentinel 0.0.0', async () => {
+        const txBuilder = factory.getAccountUpdateBuilder();
+        txBuilder.fee({ fee: testData.FEE });
+        txBuilder.source({ address: testData.ACCOUNT_1.accountId });
+        txBuilder.stakedAccountId('0.0.0');
+        txBuilder.validDuration(1000000);
+        txBuilder.node({ nodeId: '0.0.2345' });
+        txBuilder.startTime('1596110493.372646570');
+        const tx = await txBuilder.build();
+        const txJson = tx.toJson();
+        txJson.instructionsData.params.stakedAccountId.should.deepEqual('0.0.0');
+        should.not.exist(txJson.instructionsData.params.stakedNodeId);
+        tx.type.should.equal(TransactionType.AccountUpdate);
+      });
+
+      it('a stake-to-account transaction with declineReward', async () => {
+        const txBuilder = factory.getAccountUpdateBuilder();
+        txBuilder.fee({ fee: testData.FEE });
+        txBuilder.source({ address: testData.ACCOUNT_1.accountId });
+        txBuilder.stakedAccountId(testData.ACCOUNT_2.accountId);
+        txBuilder.declineStakingReward(true);
+        txBuilder.validDuration(1000000);
+        txBuilder.node({ nodeId: '0.0.2345' });
+        txBuilder.startTime('1596110493.372646570');
+        const tx = await txBuilder.build();
+        const txJson = tx.toJson();
+        txJson.instructionsData.params.stakedAccountId.should.deepEqual(testData.ACCOUNT_2.accountId);
+        txJson.instructionsData.params.declineReward.should.equal(true);
+      });
     });
 
     describe('serialized transactions', () => {
@@ -164,16 +210,54 @@ describe('HBAR Account Update Builder', () => {
         tx2.toJson().instructionsData.params.accountId.should.deepEqual(testData.ACCOUNT_1.accountId);
         tx2.toJson().instructionsData.params.stakedNodeId.should.deepEqual(NODE_ID.toString());
       });
+
+      it('a stakedAccountId transaction round-trip', async () => {
+        const txBuilder = factory.getAccountUpdateBuilder();
+        txBuilder.fee({ fee: testData.FEE });
+        txBuilder.source({ address: testData.ACCOUNT_1.accountId });
+        txBuilder.stakedAccountId(testData.ACCOUNT_2.accountId);
+        txBuilder.validDuration(1000000);
+        txBuilder.node({ nodeId: '0.0.2345' });
+        txBuilder.startTime('1596110493.372646570');
+        const tx = await txBuilder.build();
+        const serialized = tx.toBroadcastFormat();
+
+        const builder2 = factory.from(serialized);
+        const tx2 = await builder2.build();
+        tx2.type.should.equal(TransactionType.AccountUpdate);
+        tx2.toJson().instructionsData.params.stakedAccountId.should.deepEqual(testData.ACCOUNT_2.accountId);
+        should.not.exist(tx2.toJson().instructionsData.params.stakedNodeId);
+      });
     });
   });
 
   describe('should fail', () => {
-    it('a stake transaction without stakedNodeId', async () => {
+    it('a stake transaction without stakedNodeId or stakedAccountId', async () => {
       const txBuilder = factory.getAccountUpdateBuilder();
       txBuilder.fee({ fee: testData.FEE });
       txBuilder.source({ address: testData.ACCOUNT_1.accountId });
       txBuilder.node({ nodeId: '0.0.2345' });
-      await txBuilder.build().should.be.rejectedWith('Invalid transaction: missing stakedNodeId');
+      await txBuilder.build().should.be.rejectedWith('Invalid transaction: missing stakedNodeId or stakedAccountId');
+    });
+
+    it('a stake transaction with both stakedNodeId and stakedAccountId', async () => {
+      const txBuilder = factory.getAccountUpdateBuilder();
+      txBuilder.fee({ fee: testData.FEE });
+      txBuilder.source({ address: testData.ACCOUNT_1.accountId });
+      txBuilder.stakedNodeId(NODE_ID);
+      txBuilder.stakedAccountId(testData.ACCOUNT_2.accountId);
+      txBuilder.node({ nodeId: '0.0.2345' });
+      await txBuilder
+        .build()
+        .should.be.rejectedWith('Invalid transaction: cannot set both stakedNodeId and stakedAccountId');
+    });
+
+    it('a stake transaction with an invalid stakedAccountId', () => {
+      const txBuilder = factory.getAccountUpdateBuilder();
+      assert.throws(
+        () => txBuilder.stakedAccountId('invalidAccountId'),
+        (e: any) => e.message === 'Invalid stakedAccountId: invalidAccountId'
+      );
     });
 
     it('a stake transaction with an invalid account id', () => {