diff --git a/client/src/pages/CreateUserForm.test.tsx b/client/src/pages/CreateUserForm.test.tsx
new file mode 100644
index 0000000..d813eb4
--- /dev/null
+++ b/client/src/pages/CreateUserForm.test.tsx
@@ -0,0 +1,174 @@
+import { screen, waitFor } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import axios from "axios";
+import { renderWithQuery } from "@/test/render";
+import CreateUserForm from "./CreateUserForm";
+
+vi.mock("axios");
+const mockedAxios = vi.mocked(axios, { deep: true });
+
+const onSuccess = vi.fn();
+
+beforeEach(() => {
+  vi.resetAllMocks();
+});
+
+function renderForm() {
+  const user = userEvent.setup();
+  renderWithQuery(<CreateUserForm onSuccess={onSuccess} />);
+  return { user };
+}
+
+async function fillForm(
+  user: ReturnType<typeof userEvent.setup>,
+  { name = "John Doe", email = "john@example.com", password = "password123" } = {}
+) {
+  await user.type(screen.getByLabelText("Name"), name);
+  await user.type(screen.getByLabelText("Email"), email);
+  await user.type(screen.getByLabelText("Password"), password);
+}
+
+describe("CreateUserForm", () => {
+  it("should render all form fields and submit button", () => {
+    renderForm();
+
+    expect(screen.getByLabelText("Name")).toBeInTheDocument();
+    expect(screen.getByLabelText("Email")).toBeInTheDocument();
+    expect(screen.getByLabelText("Password")).toBeInTheDocument();
+    expect(screen.getByRole("button", { name: "Create User" })).toBeInTheDocument();
+  });
+
+  it("should show validation error for short name", async () => {
+    const { user } = renderForm();
+
+    await fillForm(user, { name: "Ab" });
+    await user.click(screen.getByRole("button", { name: "Create User" }));
+
+    await waitFor(() => {
+      expect(screen.getByText("Name must be at least 3 characters")).toBeInTheDocument();
+    });
+    expect(mockedAxios.post).not.toHaveBeenCalled();
+  });
+
+  it("should show validation error for short password", async () => {
+    const { user } = renderForm();
+
+    await fillForm(user, { password: "short" });
+    await user.click(screen.getByRole("button", { name: "Create User" }));
+
+    await waitFor(() => {
+      expect(screen.getByText("Password must be at least 8 characters")).toBeInTheDocument();
+    });
+    expect(mockedAxios.post).not.toHaveBeenCalled();
+  });
+
+  it("should show validation error for missing email", async () => {
+    const { user } = renderForm();
+
+    await user.type(screen.getByLabelText("Name"), "John Doe");
+    await user.type(screen.getByLabelText("Password"), "password123");
+    await user.click(screen.getByRole("button", { name: "Create User" }));
+
+    await waitFor(() => {
+      expect(screen.getByText("Invalid email address")).toBeInTheDocument();
+    });
+    expect(mockedAxios.post).not.toHaveBeenCalled();
+  });
+
+  it("should set aria-invalid on fields with errors", async () => {
+    const { user } = renderForm();
+
+    await user.click(screen.getByRole("button", { name: "Create User" }));
+
+    await waitFor(() => {
+      expect(screen.getByLabelText("Name")).toHaveAttribute("aria-invalid", "true");
+      expect(screen.getByLabelText("Password")).toHaveAttribute("aria-invalid", "true");
+    });
+  });
+
+  it("should call POST /api/users with form data on valid submit", async () => {
+    mockedAxios.post.mockResolvedValue({ data: { user: { id: "1" } } });
+    const { user } = renderForm();
+
+    await fillForm(user);
+    await user.click(screen.getByRole("button", { name: "Create User" }));
+
+    await waitFor(() => {
+      expect(mockedAxios.post).toHaveBeenCalledWith("/api/users", {
+        name: "John Doe",
+        email: "john@example.com",
+        password: "password123",
+      });
+    });
+  });
+
+  it("should call onSuccess after successful creation", async () => {
+    mockedAxios.post.mockResolvedValue({ data: { user: { id: "1" } } });
+    const { user } = renderForm();
+
+    await fillForm(user);
+    await user.click(screen.getByRole("button", { name: "Create User" }));
+
+    await waitFor(() => {
+      expect(onSuccess).toHaveBeenCalled();
+    });
+  });
+
+  it("should reset the form after successful creation", async () => {
+    mockedAxios.post.mockResolvedValue({ data: { user: { id: "1" } } });
+    const { user } = renderForm();
+
+    await fillForm(user);
+    await user.click(screen.getByRole("button", { name: "Create User" }));
+
+    await waitFor(() => {
+      expect(screen.getByLabelText("Name")).toHaveValue("");
+      expect(screen.getByLabelText("Email")).toHaveValue("");
+      expect(screen.getByLabelText("Password")).toHaveValue("");
+    });
+  });
+
+  it("should display server error message on 409 conflict", async () => {
+    const error = new Error("Conflict");
+    Object.assign(error, {
+      response: { status: 409, data: { error: "Email already exists" } },
+    });
+    mockedAxios.post.mockRejectedValue(error);
+    mockedAxios.isAxiosError.mockReturnValue(true);
+    const { user } = renderForm();
+
+    await fillForm(user);
+    await user.click(screen.getByRole("button", { name: "Create User" }));
+
+    await waitFor(() => {
+      expect(screen.getByText("Email already exists")).toBeInTheDocument();
+    });
+  });
+
+  it("should show generic error for non-Axios errors", async () => {
+    mockedAxios.post.mockRejectedValue(new Error("Network failure"));
+    mockedAxios.isAxiosError.mockReturnValue(false);
+    const { user } = renderForm();
+
+    await fillForm(user);
+    await user.click(screen.getByRole("button", { name: "Create User" }));
+
+    await waitFor(() => {
+      expect(screen.getByText("Failed to create user")).toBeInTheDocument();
+    });
+  });
+
+  it("should show 'Creating...' and disable button while submitting", async () => {
+    mockedAxios.post.mockReturnValue(new Promise(() => {}));
+    const { user } = renderForm();
+
+    await fillForm(user);
+    await user.click(screen.getByRole("button", { name: "Create User" }));
+
+    await waitFor(() => {
+      const button = screen.getByRole("button", { name: "Creating..." });
+      expect(button).toBeDisabled();
+    });
+  });
+});
diff --git a/client/src/pages/CreateUserForm.tsx b/client/src/pages/CreateUserForm.tsx
index 9f5334d..c527239 100644
--- a/client/src/pages/CreateUserForm.tsx
+++ b/client/src/pages/CreateUserForm.tsx
@@ -52,6 +52,7 @@ export default function CreateUserForm({ onSuccess }: CreateUserFormProps) {
         <Input
           id="name"
           placeholder="Full name"
+          aria-invalid={!!form.formState.errors.name}
           {...form.register("name")}
         />
         {form.formState.errors.name && (
@@ -67,6 +68,7 @@ export default function CreateUserForm({ onSuccess }: CreateUserFormProps) {
           type="email"
           placeholder="user@example.com"
           autoComplete="off"
+          aria-invalid={!!form.formState.errors.email}
           {...form.register("email")}
         />
         {form.formState.errors.email && (
@@ -82,6 +84,7 @@ export default function CreateUserForm({ onSuccess }: CreateUserFormProps) {
           type="password"
           placeholder="Minimum 8 characters"
           autoComplete="new-password"
+          aria-invalid={!!form.formState.errors.password}
           {...form.register("password")}
         />
         {form.formState.errors.password && (
diff --git a/client/src/pages/UsersPage.test.tsx b/client/src/pages/UsersPage.test.tsx
index 52b78c1..bf4fe6c 100644
--- a/client/src/pages/UsersPage.test.tsx
+++ b/client/src/pages/UsersPage.test.tsx
@@ -1,4 +1,5 @@
 import { screen, waitFor } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
 import { describe, it, expect, vi, beforeEach } from "vitest";
 import axios from "axios";
 import { renderWithQuery } from "@/test/render";
@@ -96,4 +97,48 @@ describe("UsersPage", () => {
       expect(mockedAxios.get).toHaveBeenCalledWith("/api/users");
     });
   });
+
+  it("should open the create user dialog when clicking New User", async () => {
+    mockedAxios.get.mockResolvedValue({ data: { users: [] } });
+    const user = userEvent.setup();
+    renderWithQuery(<UsersPage />);
+
+    expect(screen.queryByRole("dialog")).not.toBeInTheDocument();
+
+    await user.click(screen.getByRole("button", { name: /new user/i }));
+
+    expect(screen.getByRole("dialog")).toBeInTheDocument();
+    expect(screen.getByRole("heading", { name: "Create User" })).toBeInTheDocument();
+  });
+
+  it("should close the dialog when pressing Escape", async () => {
+    mockedAxios.get.mockResolvedValue({ data: { users: [] } });
+    const user = userEvent.setup();
+    renderWithQuery(<UsersPage />);
+
+    await user.click(screen.getByRole("button", { name: /new user/i }));
+    expect(screen.getByRole("dialog")).toBeInTheDocument();
+
+    await user.keyboard("{Escape}");
+
+    await waitFor(() => {
+      expect(screen.queryByRole("dialog")).not.toBeInTheDocument();
+    });
+  });
+
+  it("should close the dialog when clicking the overlay", async () => {
+    mockedAxios.get.mockResolvedValue({ data: { users: [] } });
+    const user = userEvent.setup();
+    renderWithQuery(<UsersPage />);
+
+    await user.click(screen.getByRole("button", { name: /new user/i }));
+    expect(screen.getByRole("dialog")).toBeInTheDocument();
+
+    const overlay = screen.getByRole("dialog").parentElement!.querySelector("[data-slot='dialog-overlay']");
+    await user.click(overlay!);
+
+    await waitFor(() => {
+      expect(screen.queryByRole("dialog")).not.toBeInTheDocument();
+    });
+  });
 });