diff --git a/extensions/signal/src/accounts.test.ts b/extensions/signal/src/accounts.test.ts
new file mode 100644
index 00000000000..91a729b56aa
--- /dev/null
+++ b/extensions/signal/src/accounts.test.ts
@@ -0,0 +1,29 @@
+import { describe, expect, it } from "vitest";
+import { resolveSignalAccount } from "./accounts.js";
+
+describe("resolveSignalAccount", () => {
+  it("uses configured defaultAccount when accountId is omitted", () => {
+    const resolved = resolveSignalAccount({
+      cfg: {
+        channels: {
+          signal: {
+            defaultAccount: "work",
+            accounts: {
+              work: {
+                name: "Work",
+                account: "+15555550123",
+                httpUrl: "http://127.0.0.1:9999",
+              },
+            },
+          },
+        },
+      } as never,
+    });
+
+    expect(resolved.accountId).toBe("work");
+    expect(resolved.name).toBe("Work");
+    expect(resolved.baseUrl).toBe("http://127.0.0.1:9999");
+    expect(resolved.config.account).toBe("+15555550123");
+    expect(resolved.configured).toBe(true);
+  });
+});
diff --git a/extensions/signal/src/accounts.ts b/extensions/signal/src/accounts.ts
index 755a3c39a5a..67b2e36934b 100644
--- a/extensions/signal/src/accounts.ts
+++ b/extensions/signal/src/accounts.ts
@@ -33,7 +33,9 @@ export function resolveSignalAccount(params: {
   cfg: OpenClawConfig;
   accountId?: string | null;
 }): ResolvedSignalAccount {
-  const accountId = normalizeAccountId(params.accountId);
+  const accountId = normalizeAccountId(
+    params.accountId ?? resolveDefaultSignalAccountId(params.cfg),
+  );
   const baseEnabled = params.cfg.channels?.signal?.enabled !== false;
   const merged = mergeSignalAccountConfig(params.cfg, accountId);
   const accountEnabled = merged.enabled !== false;