diff --git a/packages/transaction-controller/CHANGELOG.md b/packages/transaction-controller/CHANGELOG.md
index f8c38eebac4..53c78b3b8b8 100644
--- a/packages/transaction-controller/CHANGELOG.md
+++ b/packages/transaction-controller/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Harden gas fee token preflight by not treating pending gas estimates as zero-cost native gas, and by resetting `isExternalSign` when preflight validation fails ([#10071](https://github.com/MetaMask/core/pull/10071))
+
 ## [69.7.0]
 
 ### Added
diff --git a/packages/transaction-controller/src/utils/balance.test.ts b/packages/transaction-controller/src/utils/balance.test.ts
index a230667a78b..e3b145ccbbe 100644
--- a/packages/transaction-controller/src/utils/balance.test.ts
+++ b/packages/transaction-controller/src/utils/balance.test.ts
@@ -75,5 +75,40 @@ describe('Balance Utils', () => {
 
       expect(result).toBe(false);
     });
+
+    it('returns false if gas estimate is missing', async () => {
+      const result = await isNativeBalanceSufficientForGas(
+        {
+          ...TRANSACTION_META_MOCK,
+          txParams: {
+            ...TRANSACTION_META_MOCK.txParams,
+            gas: undefined,
+          },
+        },
+        MESSENGER_MOCK,
+        NETWORK_CLIENT_ID_MOCK,
+      );
+
+      expect(result).toBe(false);
+      expect(rpcRequestMock).not.toHaveBeenCalled();
+    });
+
+    it('returns false if max fee per gas is missing', async () => {
+      const result = await isNativeBalanceSufficientForGas(
+        {
+          ...TRANSACTION_META_MOCK,
+          txParams: {
+            ...TRANSACTION_META_MOCK.txParams,
+            maxFeePerGas: undefined,
+            gasPrice: undefined,
+          },
+        },
+        MESSENGER_MOCK,
+        NETWORK_CLIENT_ID_MOCK,
+      );
+
+      expect(result).toBe(false);
+      expect(rpcRequestMock).not.toHaveBeenCalled();
+    });
   });
 });
diff --git a/packages/transaction-controller/src/utils/balance.ts b/packages/transaction-controller/src/utils/balance.ts
index ae1a8cd10a1..3bb28be7c59 100644
--- a/packages/transaction-controller/src/utils/balance.ts
+++ b/packages/transaction-controller/src/utils/balance.ts
@@ -51,16 +51,22 @@ export async function isNativeBalanceSufficientForGas(
   messenger: TransactionControllerMessenger,
   networkClientId: NetworkClientId,
 ): Promise<boolean> {
-  const from = transaction.txParams.from as Hex;
+  const {
+    txParams: { from, gas, maxFeePerGas, gasPrice },
+  } = transaction;
+  const maxFeePerGasValue = maxFeePerGas ?? gasPrice;
 
-  const gasCostRawValue = new BigNumber(
-    transaction.txParams.gas ?? '0x0',
-  ).multipliedBy(
-    transaction.txParams.maxFeePerGas ?? transaction.txParams.gasPrice ?? '0x0',
-  );
+  // Gas estimates can still be in flight (e.g. skipInitialGasEstimate). Treating
+  // missing fee fields as zero makes every balance look sufficient and clears a
+  // selected gas fee token before publish.
+  if (!gas || !maxFeePerGasValue) {
+    return false;
+  }
+
+  const gasCostRawValue = new BigNumber(gas).multipliedBy(maxFeePerGasValue);
 
   const { balanceRaw } = await getNativeBalance(
-    from,
+    from as Hex,
     messenger,
     networkClientId,
   );
diff --git a/packages/transaction-controller/src/utils/gas-fee-tokens.test.ts b/packages/transaction-controller/src/utils/gas-fee-tokens.test.ts
index 6cad84fc4ec..9b769acd2da 100644
--- a/packages/transaction-controller/src/utils/gas-fee-tokens.test.ts
+++ b/packages/transaction-controller/src/utils/gas-fee-tokens.test.ts
@@ -411,10 +411,20 @@ describe('Gas Fee Tokens Utils', () => {
       request.transaction.isGasFeeTokenIgnoredIfBalance = true;
       request.transaction.selectedGasFeeToken = TOKEN_ADDRESS_1_MOCK;
       request.transaction.gasFeeTokens = [];
+      request.transaction.isExternalSign = true;
+
+      jest.mocked(request.fetchGasFeeTokens).mockResolvedValueOnce([]);
 
       await expect(checkGasFeeTokenBeforePublish(request)).rejects.toThrow(
         'Gas fee token not found and insufficient native balance',
       );
+
+      jest
+        .mocked(request.updateTransaction)
+        .mock.calls[0][1](request.transaction);
+
+      expect(request.transaction.isExternalSign).toBe(false);
+      expect(request.transaction.gasFeeTokens).toStrictEqual([]);
     });
 
     it('updates gas fee tokens', async () => {
diff --git a/packages/transaction-controller/src/utils/gas-fee-tokens.ts b/packages/transaction-controller/src/utils/gas-fee-tokens.ts
index c51dcb37ac0..849cf607098 100644
--- a/packages/transaction-controller/src/utils/gas-fee-tokens.ts
+++ b/packages/transaction-controller/src/utils/gas-fee-tokens.ts
@@ -187,6 +187,20 @@ export async function checkGasFeeTokenBeforePublish({
     isExternalSign: true,
   });
 
+  const isSelectedGasFeeTokenAvailable = gasFeeTokens?.some(
+    (token) =>
+      token.tokenAddress.toLowerCase() === selectedGasFeeToken.toLowerCase(),
+  );
+
+  if (!isSelectedGasFeeTokenAvailable) {
+    updateTransaction(transaction.id, (tx) => {
+      tx.gasFeeTokens = gasFeeTokens;
+      tx.isExternalSign = false;
+    });
+
+    throw new Error('Gas fee token not found and insufficient native balance');
+  }
+
   updateTransaction(transaction.id, (tx) => {
     tx.gasFeeTokens = gasFeeTokens;
     tx.isExternalSign = true;
@@ -194,16 +208,6 @@ export async function checkGasFeeTokenBeforePublish({
   });
 
   log('Updated gas fee tokens before publish', gasFeeTokens);
-
-  if (
-    !gasFeeTokens?.some(
-      (token) =>
-        token.tokenAddress.toLowerCase() === selectedGasFeeToken.toLowerCase(),
-    )
-  ) {
-    throw new Error('Gas fee token not found and insufficient native balance');
-  }
-
   log('Publishing with selected gas fee token', { selectedGasFeeToken });
 }