diff --git a/packages/sdk/src/actions/getFillByDepositTx.ts b/packages/sdk/src/actions/getFillByDepositTx.ts
index 875f7c9..eb78d37 100644
--- a/packages/sdk/src/actions/getFillByDepositTx.ts
+++ b/packages/sdk/src/actions/getFillByDepositTx.ts
@@ -9,7 +9,7 @@ import {
   TransactionReceipt,
 } from "viem";
 import { MAINNET_INDEXER_API } from "../constants/index.js";
-import { NoFillLogError } from "../errors/index.js";
+import { NoFillLogError, WaitForFillTimeoutError } from "../errors/index.js";
 import { FillEventLog, IndexerStatusResponse } from "../types/index.js";
 import { parseFillLogs } from "./waitForFillTx.js";
 
@@ -127,26 +127,60 @@ export type FillStatus = {
   parsedFillEvent: FillEventLog;
 };
 
+// Default max wait for a fill before rejecting (5 minutes).
+export const DEFAULT_WAIT_FOR_FILL_TIMEOUT_MS = 300_000;
+
 export async function waitForFillByDepositTx(
   params: GetFillByDepositTxParams & {
     pollingInterval?: number;
+    timeout?: number;
   },
 ): ReturnType<typeof getFillByDepositTx> {
   const interval =
-    params?.pollingInterval ?? params.destinationChainClient.pollingInterval;
+    params.pollingInterval ?? params.destinationChainClient.pollingInterval;
+  const timeoutMs = params.timeout ?? DEFAULT_WAIT_FOR_FILL_TIMEOUT_MS;
+  const deadline = Date.now() + timeoutMs;
 
-  return new Promise((res) => {
+  return new Promise((resolve, reject) => {
     const poll = () => {
       getFillByDepositTx(params)
         .then((response) => {
           if (response.fillTxReceipt) {
-            res(response);
-          } else {
-            setTimeout(poll, interval);
+            resolve(response);
+            return;
+          }
+
+          if (Date.now() >= deadline) {
+            reject(
+              new WaitForFillTimeoutError(
+                BigInt(params.deposit.depositId),
+                params.deposit.destinationChainId,
+                timeoutMs,
+                params.deposit.depositTxHash,
+              ),
+            );
+            return;
           }
+
+          setTimeout(poll, interval);
         })
         .catch((error) => {
-          params?.logger ? params.logger.error(error) : console.log(error);
+          params.logger ? params.logger.error(error) : console.log(error);
+
+          if (Date.now() >= deadline) {
+            reject(
+              error instanceof NoFillLogError
+                ? new WaitForFillTimeoutError(
+                    BigInt(params.deposit.depositId),
+                    params.deposit.destinationChainId,
+                    timeoutMs,
+                    params.deposit.depositTxHash,
+                  )
+                : error,
+            );
+            return;
+          }
+
           setTimeout(poll, interval);
         });
     };
diff --git a/packages/sdk/src/errors/index.ts b/packages/sdk/src/errors/index.ts
index 4d23831..edc5995 100644
--- a/packages/sdk/src/errors/index.ts
+++ b/packages/sdk/src/errors/index.ts
@@ -136,3 +136,18 @@ export class NoFillLogError extends Error {
     this.name = "Fill Log Not Found";
   }
 }
+
+export class WaitForFillTimeoutError extends Error {
+  constructor(
+    depositId: bigint,
+    chainId: number,
+    timeoutMs: number,
+    depositTxHash?: Hash,
+  ) {
+    super(
+      `Timed out after ${timeoutMs}ms waiting for fill on chain ${chainId} for deposit id #${depositId.toString()}${depositTxHash ? ` with depositTxHash ${depositTxHash}` : "."}`,
+    );
+    this.name = "WaitForFillTimeout";
+  }
+}
+
diff --git a/packages/sdk/test/unit/actions/waitForFillByDepositTx.test.ts b/packages/sdk/test/unit/actions/waitForFillByDepositTx.test.ts
new file mode 100644
index 0000000..4e34f53
--- /dev/null
+++ b/packages/sdk/test/unit/actions/waitForFillByDepositTx.test.ts
@@ -0,0 +1,57 @@
+import { afterEach, beforeEach, describe, expect, test, vi } from "vitest";
+import {
+  waitForFillByDepositTx,
+  DEFAULT_WAIT_FOR_FILL_TIMEOUT_MS,
+} from "../../../src/actions/getFillByDepositTx.js";
+import { WaitForFillTimeoutError } from "../../../src/errors/index.js";
+import type { PublicClient } from "viem";
+
+describe("waitForFillByDepositTx", () => {
+  beforeEach(() => {
+    vi.stubGlobal(
+      "fetch",
+      vi.fn().mockRejectedValue(new Error("indexer unavailable")),
+    );
+  });
+
+  afterEach(() => {
+    vi.unstubAllGlobals();
+  });
+
+  test("rejects with WaitForFillTimeoutError when no fill appears before timeout", async () => {
+    const destinationChainClient = {
+      pollingInterval: 20,
+      getLogs: vi.fn().mockResolvedValue([]),
+      getTransactionReceipt: vi.fn(),
+      getBlock: vi.fn(),
+    } as unknown as PublicClient;
+
+    await expect(
+      waitForFillByDepositTx({
+        deposit: {
+          depositId: 42n,
+          originChainId: 1,
+          destinationChainId: 10,
+          destinationSpokePoolAddress:
+            "0x0000000000000000000000000000000000000001",
+          message: "0x",
+        },
+        destinationChainClient,
+        indexerUrl: "http://127.0.0.1:9",
+        timeout: 80,
+        pollingInterval: 20,
+        logger: {
+          error: vi.fn(),
+          warn: vi.fn(),
+          debug: vi.fn(),
+          info: vi.fn(),
+        },
+      }),
+    ).rejects.toBeInstanceOf(WaitForFillTimeoutError);
+  });
+
+  test("exports a finite default timeout so callers are not left polling forever", () => {
+    expect(DEFAULT_WAIT_FOR_FILL_TIMEOUT_MS).toBeGreaterThan(0);
+    expect(DEFAULT_WAIT_FOR_FILL_TIMEOUT_MS).toBe(300_000);
+  });
+});