diff --git a/db/setup.php b/db/setup.php
index ef76881..c16c8d3 100644
--- a/db/setup.php
+++ b/db/setup.php
@@ -10,13 +10,21 @@ try {
     $pdo->exec("
         CREATE TABLE IF NOT EXISTS `users` (
           `id` INT AUTO_INCREMENT PRIMARY KEY,
-          `username` VARCHAR(255) NOT NULL UNIQUE,
+          `username` VARCHAR(255) NOT NULL,
+          `email` VARCHAR(255) NOT NULL UNIQUE,
           `password` VARCHAR(255) NOT NULL,
           `role` VARCHAR(50) NOT NULL,
+          `birth_date` DATE,
           `created_at` TIMESTAMP DEFAULT CURRENT_TIMESTAMP
         ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
     ");
 
+    // Add columns if they don't exist
+    try { $pdo->exec("ALTER TABLE `users` ADD COLUMN `email` VARCHAR(255) NOT NULL UNIQUE AFTER `username`"); } catch (PDOException $e) { /* Ignore */ }
+    try { $pdo->exec("ALTER TABLE `users` ADD COLUMN `birth_date` DATE AFTER `role`"); } catch (PDOException $e) { /* Ignore */ }
+    // We can't easily remove the unique constraint in a single command that works on all versions, so we'll leave it for now.
+    // The signup logic will handle this by checking for existing usernames.
+
     // Create clubs table
     $pdo->exec("
         CREATE TABLE IF NOT EXISTS `clubs` (
@@ -49,12 +57,14 @@ try {
     } else {
         // Insert default superadmin user
         $username = 'superadmin';
+        $email = 'superadmin@picklepro.com';
         $password = 'superadmin'; // Default password, you should change this
         $hashed_password = password_hash($password, PASSWORD_DEFAULT);
         $role = 'superadmin';
 
-        $stmt = $pdo->prepare("INSERT INTO users (username, password, role) VALUES (:username, :password, :role)");
+        $stmt = $pdo->prepare("INSERT INTO users (username, email, password, role) VALUES (:username, :email, :password, :role)");
         $stmt->bindParam(':username', $username);
+        $stmt->bindParam(':email', $email);
         $stmt->bindParam(':password', $hashed_password);
         $stmt->bindParam(':role', $role);
         $stmt->execute();
diff --git a/index.php b/index.php
index fc0c99b..3c594a5 100644
--- a/index.php
+++ b/index.php
@@ -61,7 +61,9 @@
                         <a href="logout.php" class="btn btn-outline-primary">Sair</a>
                     <?php else: ?>
                         <a href="/login.php" class="btn btn-link text-decoration-none me-2">Entrar</a>
-                        <a href="#" class="btn btn-primary">Cadastrar</a>
+                        <button type="button" class="btn btn-primary" data-bs-toggle="modal" data-bs-target="#signupModal">
+                            Cadastrar
+                        </button>
                     <?php endif; ?>
                 </div>
             </div>
@@ -70,6 +72,16 @@
 
     <!-- Main Content -->
     <main class="container my-4">
+        <?php if (isset($_SESSION['error_message'])): ?>
+            <div class="alert alert-danger" role="alert">
+                <?php echo $_SESSION['error_message']; unset($_SESSION['error_message']); ?>
+            </div>
+        <?php endif; ?>
+        <?php if (isset($_SESSION['success_message'])): ?>
+            <div class="alert alert-success" role="alert">
+                <?php echo $_SESSION['success_message']; unset($_SESSION['success_message']); ?>
+            </div>
+        <?php endif; ?>
         <div class="text-center mb-5">
             <h1 class="display-5 fw-bold">Seu Portal Completo de <span class="text-primary">Pickleball</span></h1>
         </div>
@@ -167,6 +179,43 @@
         </div>
     </footer>
 
+    <!-- Signup Modal -->
+    <div class="modal fade" id="signupModal" tabindex="-1" aria-labelledby="signupModalLabel" aria-hidden="true">
+        <div class="modal-dialog">
+            <div class="modal-content">
+                <div class="modal-header">
+                    <h5 class="modal-title" id="signupModalLabel">Cadastro de Atleta</h5>
+                    <button type="button" class="btn-close" data-bs-dismiss="modal" aria-label="Close"></button>
+                </div>
+                <div class="modal-body">
+                    <form action="signup.php" method="POST">
+                        <div class="mb-3">
+                            <label for="fullName" class="form-label">Nome Completo</label>
+                            <input type="text" class="form-control" id="fullName" name="fullName" required>
+                        </div>
+                        <div class="mb-3">
+                            <label for="birthDate" class="form-label">Data de Nascimento</label>
+                            <input type="date" class="form-control" id="birthDate" name="birthDate" required>
+                        </div>
+                        <div class="mb-3">
+                            <label for="email" class="form-label">E-mail</label>
+                            <input type="email" class="form-control" id="email" name="email" required>
+                        </div>
+                        <div class="mb-3">
+                            <label for="password" class="form-label">Senha</label>
+                            <input type="password" class="form-control" id="password" name="password" required>
+                        </div>
+                        <div class="mb-3">
+                            <label for="confirmPassword" class="form-label">Confirmar Senha</label>
+                            <input type="password" class="form-control" id="confirmPassword" name="confirmPassword" required>
+                        </div>
+                        <button type="submit" class="btn btn-primary w-100">Cadastrar</button>
+                    </form>
+                </div>
+            </div>
+        </div>
+    </div>
+
     <!-- Scripts -->
     <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/js/bootstrap.bundle.min.js"></script>
     <script src="assets/js/main.js?v=<?php echo time(); ?>"></script>
diff --git a/signup.php b/signup.php
new file mode 100644
index 0000000..b70f662
--- /dev/null
+++ b/signup.php
@@ -0,0 +1,58 @@
+<?php
+session_start();
+require_once 'db/config.php';
+
+if ($_SERVER['REQUEST_METHOD'] === 'POST') {
+    $fullName = $_POST['fullName'] ?? '';
+    $birthDate = $_POST['birthDate'] ?? '';
+    $email = $_POST['email'] ?? '';
+    $password = $_POST['password'] ?? '';
+    $confirmPassword = $_POST['confirmPassword'] ?? '';
+
+    // Validation
+    if (empty($fullName) || empty($birthDate) || empty($email) || empty($password) || empty($confirmPassword)) {
+        $_SESSION['error_message'] = 'Todos os campos são obrigatórios.';
+        header('Location: index.php');
+        exit;
+    }
+
+    if ($password !== $confirmPassword) {
+        $_SESSION['error_message'] = 'As senhas não correspondem.';
+        header('Location: index.php');
+        exit;
+    }
+
+    if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
+        $_SESSION['error_message'] = 'Formato de e-mail inválido.';
+        header('Location: index.php');
+        exit;
+    }
+
+    try {
+        $pdo = db();
+
+        // Check if user already exists
+        $stmt = $pdo->prepare('SELECT id FROM users WHERE email = ?');
+        $stmt->execute([$email]);
+        if ($stmt->fetch()) {
+            $_SESSION['error_message'] = 'Este e-mail já está cadastrado.';
+            header('Location: index.php');
+            exit;
+        }
+
+        // Insert new user
+        $hashedPassword = password_hash($password, PASSWORD_DEFAULT);
+        $stmt = $pdo->prepare('INSERT INTO users (username, email, password, role, birth_date) VALUES (?, ?, ?, ?, ?)');
+        $stmt->execute([$fullName, $email, $hashedPassword, 'atleta', $birthDate]);
+
+        $_SESSION['success_message'] = 'Cadastro realizado com sucesso! Você já pode fazer o login.';
+        header('Location: index.php');
+        exit;
+
+    } catch (PDOException $e) {
+        $_SESSION['error_message'] = 'Erro no banco de dados. Tente novamente mais tarde.';
+        // In a real app, you would log this error: error_log($e->getMessage());
+        header('Location: index.php');
+        exit;
+    }
+}