diff --git a/components/keys/VoteModal.tsx b/components/keys/VoteModal.tsx
index 09ef691..60dccf5 100644
--- a/components/keys/VoteModal.tsx
+++ b/components/keys/VoteModal.tsx
@@ -44,13 +44,18 @@ export function VoteModal({
 
   const handleSubmit = async () => {
     if (!address || selectedOption === null) return;
-    await voteMutation.mutateAsync({
-      proposalId: proposal.id,
-      optionIndex: selectedOption,
-      walletAddress: address,
-      token: jwt,
-    });
-    setRecorded(true);
+    try {
+      await voteMutation.mutateAsync({
+        proposalId: proposal.id,
+        optionIndex: selectedOption,
+        walletAddress: address,
+        token: jwt,
+      });
+      setRecorded(true);
+    } catch {
+      // react-query exposes the rejection as voteMutation.error so the error
+      // message below can be rendered; nothing else to do here.
+    }
   };
 
   return (
@@ -109,6 +114,17 @@ export function VoteModal({
             </p>
           )}
 
+          {voteMutation.isError && (
+            <p
+              data-testid="vote-error-message"
+              className="text-sm font-medium text-red-600"
+            >
+              {voteMutation.error instanceof Error
+                ? voteMutation.error.message
+                : "Vote submission failed. Please try again."}
+            </p>
+          )}
+
           <div className="flex justify-end gap-3">
             <Button
               type="button"
diff --git a/components/keys/__tests__/VoteModal.test.tsx b/components/keys/__tests__/VoteModal.test.tsx
new file mode 100644
index 0000000..7524d01
--- /dev/null
+++ b/components/keys/__tests__/VoteModal.test.tsx
@@ -0,0 +1,147 @@
+import { describe, expect, it, vi, beforeEach } from "vitest";
+import { render, screen } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { VoteModal } from "../VoteModal";
+import type { GovernanceProposal } from "@/lib/api";
+
+vi.mock("@/hooks/useAuth", () => ({
+  useAuth: () => ({
+    address: "GVOTER123",
+    jwt: "token-123",
+  }),
+}));
+
+const mutateAsync = vi.fn();
+
+let mockIsPending = false;
+let mockIsError = false;
+let mockError: unknown = null;
+const reset = vi.fn();
+
+vi.mock("@/hooks/useCreatorKeys", () => ({
+  useCastGovernanceVoteMutation: () => ({
+    mutateAsync,
+    isPending: mockIsPending,
+    isError: mockIsError,
+    error: mockError,
+    reset,
+  }),
+}));
+
+const proposal: GovernanceProposal = {
+  id: "proposal-1",
+  title: "Should we ship v2?",
+  status: "active",
+  expires_at: "2030-01-01T00:00:00Z",
+  user_voting_weight: 1000,
+  user_has_voted: false,
+  options: [
+    { label: "Yes", vote_weight: 100 },
+    { label: "No", vote_weight: 100 },
+  ],
+};
+
+const onOpenChange = vi.fn();
+
+function renderModal() {
+  return render(
+    <VoteModal
+      keyId="key-1"
+      proposal={proposal}
+      open
+      onOpenChange={onOpenChange}
+    />
+  );
+}
+
+describe("VoteModal", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    mutateAsync.mockResolvedValue(undefined);
+    mockIsPending = false;
+    mockIsError = false;
+    mockError = null;
+  });
+
+  it("disables the Confirm button until an option is selected", () => {
+    renderModal();
+    expect(screen.getByRole("button", { name: /confirm vote/i })).toBeDisabled();
+  });
+
+  it("submits option index 0 when the first option is selected and confirmed", async () => {
+    const user = userEvent.setup();
+    renderModal();
+
+    await user.click(screen.getAllByRole("radio")[0]);
+    await user.click(screen.getByRole("button", { name: /confirm vote/i }));
+
+    expect(mutateAsync).toHaveBeenCalledExactlyOnceWith({
+      proposalId: "proposal-1",
+      optionIndex: 0,
+      walletAddress: "GVOTER123",
+      token: "token-123",
+    });
+  });
+
+  it("submits option index 1 when the second option is selected and confirmed", async () => {
+    const user = userEvent.setup();
+    renderModal();
+
+    await user.click(screen.getAllByRole("radio")[1]);
+    await user.click(screen.getByRole("button", { name: /confirm vote/i }));
+
+    expect(mutateAsync).toHaveBeenCalledExactlyOnceWith({
+      proposalId: "proposal-1",
+      optionIndex: 1,
+      walletAddress: "GVOTER123",
+      token: "token-123",
+    });
+  });
+
+  it("disables the Confirm button once an option is selected", async () => {
+    const user = userEvent.setup();
+    renderModal();
+
+    await user.click(screen.getAllByRole("radio")[0]);
+    expect(screen.getByRole("button", { name: /confirm vote/i })).toBeEnabled();
+  });
+
+  it("disables the Confirm button and shows 'Vote recorded' after a successful submission", async () => {
+    const user = userEvent.setup();
+    renderModal();
+
+    await user.click(screen.getAllByRole("radio")[0]);
+    await user.click(screen.getByRole("button", { name: /confirm vote/i }));
+
+    expect(
+      screen.getByText("Your vote has been recorded")
+    ).toBeInTheDocument();
+    expect(screen.getByRole("button", { name: /confirm vote/i })).toBeDisabled();
+  });
+
+  it("shows an error message and re-enables the Confirm button after a failed submission", async () => {
+    mutateAsync.mockRejectedValueOnce(new Error("Contract reverted"));
+    const user = userEvent.setup();
+    const { rerender } = renderModal();
+
+    await user.click(screen.getAllByRole("radio")[1]);
+    await user.click(screen.getByRole("button", { name: /confirm vote/i }));
+
+    mockIsError = true;
+    mockError = new Error("Contract reverted");
+    rerender(
+      <VoteModal
+        keyId="key-1"
+        proposal={proposal}
+        open
+        onOpenChange={onOpenChange}
+      />
+    );
+
+    expect(
+      screen.getByTestId("vote-error-message")
+    ).toHaveTextContent("Contract reverted");
+    expect(screen.getByRole("button", { name: /confirm vote/i })).toBeEnabled();
+    expect(screen.queryByText("Your vote has been recorded")).not.toBeInTheDocument();
+  });
+});