diff --git a/packages/transaction-controller/CHANGELOG.md b/packages/transaction-controller/CHANGELOG.md
index eb181b8f82..c5b5392900 100644
--- a/packages/transaction-controller/CHANGELOG.md
+++ b/packages/transaction-controller/CHANGELOG.md
@@ -7,6 +7,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Include Mantle operator fee in the displayed L1 gas estimate when simulated `gasUsed` is unavailable, by falling back to the transaction's gas limit ([#8837](https://github.com/MetaMask/core/pull/8837))
+  - Adds a `protected getOperatorFeeGas` hook on `OracleLayer1GasFeeFlow` that subclasses can override to supply a fallback value. The default behaviour is unchanged (returns `transactionMeta.gasUsed`).
+  - `MantleLayer1GasFeeFlow` overrides the hook with `gasUsed ?? txParams.gas ?? txParams.gasLimit`, so the operator-fee oracle is called with the gas limit when `gasUsed` is missing. Gas limit is an upper bound on actual gas used, so the operator fee is over-estimated rather than under-reported.
+
 ## [66.0.0]
 
 ### Changed
diff --git a/packages/transaction-controller/src/gas-flows/MantleLayer1GasFeeFlow.test.ts b/packages/transaction-controller/src/gas-flows/MantleLayer1GasFeeFlow.test.ts
index 5980118a4e..e6528702e9 100644
--- a/packages/transaction-controller/src/gas-flows/MantleLayer1GasFeeFlow.test.ts
+++ b/packages/transaction-controller/src/gas-flows/MantleLayer1GasFeeFlow.test.ts
@@ -180,7 +180,85 @@ describe('MantleLayer1GasFeeFlow', () => {
       });
     });
 
-    it('returns converted L1 fee when no gasUsed (no operator fee)', async () => {
+    it('falls back to txParams.gas for operator fee when gasUsed is missing', async () => {
+      contractGetOperatorFeeMock.mockResolvedValueOnce(
+        bnFromHex(OPERATOR_FEE_MOCK),
+      );
+
+      jest
+        .spyOn(TransactionFactory, 'fromTxData')
+        .mockReturnValueOnce(
+          createMockTypedTransaction(
+            Buffer.from(SERIALIZED_TRANSACTION_MOCK, 'hex'),
+          ),
+        );
+
+      const flow = new MantleLayer1GasFeeFlow();
+      const response = await flow.getLayer1Fee(request);
+
+      const expectedL1FeeInMnt = bnFromHex(L1_FEE_MOCK).mul(TOKEN_RATIO_MOCK);
+      const expectedTotal = expectedL1FeeInMnt.add(
+        bnFromHex(OPERATOR_FEE_MOCK),
+      );
+
+      expect(contractGetOperatorFeeMock).toHaveBeenCalledTimes(1);
+      expect(contractGetOperatorFeeMock).toHaveBeenCalledWith(
+        TRANSACTION_PARAMS_MOCK.gas,
+      );
+      expect(response).toStrictEqual({
+        layer1Fee: add0x(padHexToEvenLength(expectedTotal.toString(16))),
+      });
+    });
+
+    it('falls back to txParams.gasLimit for operator fee when gasUsed and txParams.gas are missing', async () => {
+      const gasLimit = '0x9999';
+      request = {
+        ...request,
+        transactionMeta: {
+          ...request.transactionMeta,
+          txParams: {
+            from: TRANSACTION_PARAMS_MOCK.from,
+            gasLimit,
+          },
+        },
+      };
+
+      contractGetOperatorFeeMock.mockResolvedValueOnce(
+        bnFromHex(OPERATOR_FEE_MOCK),
+      );
+
+      jest
+        .spyOn(TransactionFactory, 'fromTxData')
+        .mockReturnValueOnce(
+          createMockTypedTransaction(
+            Buffer.from(SERIALIZED_TRANSACTION_MOCK, 'hex'),
+          ),
+        );
+
+      const flow = new MantleLayer1GasFeeFlow();
+      const response = await flow.getLayer1Fee(request);
+
+      const expectedL1FeeInMnt = bnFromHex(L1_FEE_MOCK).mul(TOKEN_RATIO_MOCK);
+      const expectedTotal = expectedL1FeeInMnt.add(
+        bnFromHex(OPERATOR_FEE_MOCK),
+      );
+
+      expect(contractGetOperatorFeeMock).toHaveBeenCalledTimes(1);
+      expect(contractGetOperatorFeeMock).toHaveBeenCalledWith(gasLimit);
+      expect(response).toStrictEqual({
+        layer1Fee: add0x(padHexToEvenLength(expectedTotal.toString(16))),
+      });
+    });
+
+    it('skips operator fee when no gasUsed, txParams.gas, or txParams.gasLimit is available', async () => {
+      request = {
+        ...request,
+        transactionMeta: {
+          ...request.transactionMeta,
+          txParams: { from: TRANSACTION_PARAMS_MOCK.from },
+        },
+      };
+
       jest
         .spyOn(TransactionFactory, 'fromTxData')
         .mockReturnValueOnce(
diff --git a/packages/transaction-controller/src/gas-flows/MantleLayer1GasFeeFlow.ts b/packages/transaction-controller/src/gas-flows/MantleLayer1GasFeeFlow.ts
index d353659c83..faae3cf509 100644
--- a/packages/transaction-controller/src/gas-flows/MantleLayer1GasFeeFlow.ts
+++ b/packages/transaction-controller/src/gas-flows/MantleLayer1GasFeeFlow.ts
@@ -46,6 +46,16 @@ export class MantleLayer1GasFeeFlow extends OracleLayer1GasFeeFlow {
     return MANTLE_CHAIN_IDS.includes(transactionMeta.chainId);
   }
 
+  protected override getOperatorFeeGas(
+    transactionMeta: TransactionMeta,
+  ): string | undefined {
+    return (
+      transactionMeta.gasUsed ??
+      transactionMeta.txParams.gas ??
+      transactionMeta.txParams.gasLimit
+    );
+  }
+
   protected override async transformOracleFee(
     oracleFee: BN,
     request: Layer1GasFeeFlowRequest,
diff --git a/packages/transaction-controller/src/gas-flows/OracleLayer1GasFeeFlow.ts b/packages/transaction-controller/src/gas-flows/OracleLayer1GasFeeFlow.ts
index 21bcb2c14f..e76586b2a7 100644
--- a/packages/transaction-controller/src/gas-flows/OracleLayer1GasFeeFlow.ts
+++ b/packages/transaction-controller/src/gas-flows/OracleLayer1GasFeeFlow.ts
@@ -174,18 +174,33 @@ export abstract class OracleLayer1GasFeeFlow implements Layer1GasFeeFlow {
     return toBN(result);
   }
 
+  /**
+   * Returns the gas value to pass to the operator-fee oracle, or undefined
+   * to skip the operator-fee call entirely. Defaults to the simulated
+   * `gasUsed` on the transaction. Subclasses can override to supply a
+   * fallback (e.g. estimated gas limit) when `gasUsed` is unavailable.
+   *
+   * @param transactionMeta - The transaction metadata.
+   * @returns The gas value, or undefined to skip the operator-fee call.
+   */
+  protected getOperatorFeeGas(
+    transactionMeta: TransactionMeta,
+  ): string | undefined {
+    return transactionMeta.gasUsed;
+  }
+
   async #getOperatorLayer1GasFee(
     contract: Contract,
     transactionMeta: TransactionMeta,
   ): Promise<BN> {
-    const { gasUsed } = transactionMeta;
+    const gas = this.getOperatorFeeGas(transactionMeta);
 
-    if (!gasUsed) {
+    if (!gas) {
       return ZERO;
     }
 
     try {
-      const result = await contract.getOperatorFee(gasUsed);
+      const result = await contract.getOperatorFee(gas);
 
       if (result === undefined) {
         return ZERO;