diff --git a/src/FirstPayment/FirstPaymentHandler.php b/src/FirstPayment/FirstPaymentHandler.php
index 7e965d5..0977dab 100644
--- a/src/FirstPayment/FirstPaymentHandler.php
+++ b/src/FirstPayment/FirstPaymentHandler.php
@@ -21,6 +21,9 @@ class FirstPaymentHandler
     /** @var \Illuminate\Support\Collection */
     protected $actions;
 
+    /** @var bool */
+    protected $alreadyProcessed = false;
+
     /**
      * FirstPaymentHandler constructor.
      *
@@ -40,7 +43,20 @@ public function __construct(MolliePayment $molliePayment)
      */
     public function execute()
     {
+        $this->alreadyProcessed = false;
+
         $order = DB::transaction(function () {
+            $localPayment = Cashier::$paymentModel::query()
+                ->where('mollie_payment_id', $this->molliePayment->id)
+                ->lockForUpdate()
+                ->first();
+
+            if ($localPayment?->order) {
+                $this->alreadyProcessed = true;
+
+                return $localPayment->order;
+            }
+
             $this->owner->mollie_mandate_id = $this->molliePayment->mandateId;
             $this->owner->save();
 
@@ -53,7 +69,7 @@ public function execute()
 
             // It's possible a payment from Cashier v1 is not yet tracked in the Cashier database.
             // In that case we create a record here.
-            $localPayment = Cashier::$paymentModel::findByMolliePaymentOrCreate(
+            $localPayment = $localPayment ?: Cashier::$paymentModel::findByMolliePaymentOrCreate(
                 $this->molliePayment,
                 $this->owner,
                 $this->actions->all()
@@ -68,11 +84,23 @@ public function execute()
             return $order;
         });
 
-        event(new MandateUpdated($this->owner, $this->molliePayment));
+        if (! $this->alreadyProcessed) {
+            event(new MandateUpdated($this->owner, $this->molliePayment));
+        }
 
         return $order;
     }
 
+    /**
+     * Determine if execute() returned an already processed first payment.
+     *
+     * @return bool
+     */
+    public function wasAlreadyProcessed()
+    {
+        return $this->alreadyProcessed;
+    }
+
     /**
      * Fetch the owner model using the mandate payment metadata.
      *
diff --git a/src/Http/Controllers/FirstPaymentWebhookController.php b/src/Http/Controllers/FirstPaymentWebhookController.php
index 0ac47d9..39e15af 100644
--- a/src/Http/Controllers/FirstPaymentWebhookController.php
+++ b/src/Http/Controllers/FirstPaymentWebhookController.php
@@ -24,7 +24,13 @@ public function handleWebhook(Request $request)
 
         if ($payment) {
             if ($payment->isPaid()) {
-                $order = (new FirstPaymentHandler($payment))->execute();
+                $handler = new FirstPaymentHandler($payment);
+                $order = $handler->execute();
+
+                if ($handler->wasAlreadyProcessed()) {
+                    return new Response(null, 200);
+                }
+
                 $payment->webhookUrl = route('webhooks.mollie.aftercare');
 
                 /** @var UpdateMolliePayment $updateMolliePayment */
diff --git a/tests/SubscriptionBuilder/FirstPaymentSubscriptionBuilderTest.php b/tests/SubscriptionBuilder/FirstPaymentSubscriptionBuilderTest.php
index 3e34d59..caeaa01 100644
--- a/tests/SubscriptionBuilder/FirstPaymentSubscriptionBuilderTest.php
+++ b/tests/SubscriptionBuilder/FirstPaymentSubscriptionBuilderTest.php
@@ -132,45 +132,7 @@ public function handlesAPaidFirstPayment()
 
         Event::fake();
 
-        $molliePayment = new MolliePayment(new MollieApiClient);
-        $molliePayment->id = 'tr_unique_payment_id';
-        $molliePayment->paidAt = Carbon::now()->toIso8601String();
-        $molliePayment->mandateId = 'mdt_unique_mandate_id';
-        $molliePayment->amount = (object) [
-            'currency' => 'EUR',
-            'value' => '0.05',
-        ];
-        $molliePayment->metadata = json_decode(json_encode([
-            'owner' => [
-                'type' => get_class($this->user),
-                'id' => 1,
-            ],
-            'actions' => [
-                [
-                    'handler' => StartSubscription::class,
-                    'description' => 'Monthly payment',
-                    'subtotal' => [
-                        'value' => '0.00',
-                        'currency' => 'EUR',
-                    ],
-                    'taxPercentage' => 20,
-                    'plan' => 'monthly-10-1',
-                    'name' => 'default',
-                    'quantity' => 1,
-                    'nextPaymentAt' => now()->addDays(12)->toIso8601String(),
-                    'trialUntil' => now()->addDays(5)->toIso8601String(),
-                ],
-                [
-                    'handler' => AddGenericOrderItem::class,
-                    'description' => 'Test mandate payment',
-                    'subtotal' => [
-                        'value' => '0.04',
-                        'currency' => 'EUR',
-                    ],
-                    'taxPercentage' => 20,
-                ],
-            ],
-        ]));
+        $molliePayment = $this->getPaidFirstPayment();
 
         Cashier::$paymentModel::createFromMolliePayment($molliePayment, $this->user);
 
@@ -208,6 +170,41 @@ public function handlesAPaidFirstPayment()
         $this->assertSame(Order::first()->items->first()->description_extra_lines[0], 'From 2019-01-01 to 2019-02-01');
     }
 
+    #[Test]
+    public function ignoresADuplicatePaidFirstPaymentWebhook()
+    {
+        Event::fake();
+
+        $molliePayment = $this->getPaidFirstPayment();
+
+        Cashier::$paymentModel::createFromMolliePayment($molliePayment, $this->user);
+
+        $this->withMockedGetMolliePayment(2, $molliePayment);
+        $this->withMockedGetMollieMandateAccepted(2);
+        $this->withMockedGetMollieCustomer(2);
+        $this->withMockedUpdateMolliePayment();
+
+        $firstResponse = $this->post(route('webhooks.mollie.first_payment', [
+            'id' => 'tr_unique_payment_id',
+        ]));
+
+        $secondResponse = $this->post(route('webhooks.mollie.first_payment', [
+            'id' => 'tr_unique_payment_id',
+        ]));
+
+        $firstResponse->assertStatus(200);
+        $secondResponse->assertStatus(200);
+
+        $this->assertSame(1, Order::count());
+        $this->assertSame(1, Order::query()->where('mollie_payment_id', 'tr_unique_payment_id')->count());
+        $this->assertSame(1, Cashier::$paymentModel::count());
+        $this->assertNotNull(Cashier::$paymentModel::first()->order_id);
+
+        Event::assertDispatched(OrderProcessed::class, 1);
+        Event::assertDispatched(FirstPaymentPaid::class, 1);
+        Event::assertDispatched(SubscriptionStarted::class, 1);
+    }
+
     #[Test]
     public function testWithCouponNoTrialValidatesCoupon()
     {
@@ -270,6 +267,51 @@ public function testHandlesNoTrialMode()
         );
     }
 
+    protected function getPaidFirstPayment(): MolliePayment
+    {
+        $molliePayment = new MolliePayment(new MollieApiClient);
+        $molliePayment->id = 'tr_unique_payment_id';
+        $molliePayment->paidAt = Carbon::now()->toIso8601String();
+        $molliePayment->mandateId = 'mdt_unique_mandate_id';
+        $molliePayment->amount = (object) [
+            'currency' => 'EUR',
+            'value' => '0.05',
+        ];
+        $molliePayment->metadata = json_decode(json_encode([
+            'owner' => [
+                'type' => get_class($this->user),
+                'id' => 1,
+            ],
+            'actions' => [
+                [
+                    'handler' => StartSubscription::class,
+                    'description' => 'Monthly payment',
+                    'subtotal' => [
+                        'value' => '0.00',
+                        'currency' => 'EUR',
+                    ],
+                    'taxPercentage' => 20,
+                    'plan' => 'monthly-10-1',
+                    'name' => 'default',
+                    'quantity' => 1,
+                    'nextPaymentAt' => now()->addDays(12)->toIso8601String(),
+                    'trialUntil' => now()->addDays(5)->toIso8601String(),
+                ],
+                [
+                    'handler' => AddGenericOrderItem::class,
+                    'description' => 'Test mandate payment',
+                    'subtotal' => [
+                        'value' => '0.04',
+                        'currency' => 'EUR',
+                    ],
+                    'taxPercentage' => 20,
+                ],
+            ],
+        ]));
+
+        return $molliePayment;
+    }
+
     /**
      * @return \Laravel\Cashier\SubscriptionBuilder\FirstPaymentSubscriptionBuilder
      */
diff --git a/tests/UpdatePaymentMethod/UpdatePaymentMethodTest.php b/tests/UpdatePaymentMethod/UpdatePaymentMethodTest.php
index a8165f1..c49ed53 100644
--- a/tests/UpdatePaymentMethod/UpdatePaymentMethodTest.php
+++ b/tests/UpdatePaymentMethod/UpdatePaymentMethodTest.php
@@ -66,6 +66,38 @@ public function canUpdatePaymentMethod()
         });
     }
 
+    #[Test]
+    public function doesNotAddBalanceAgainForADuplicateFirstPayment()
+    {
+        $owner = User::factory()->create([
+            'mollie_mandate_id' => 'mdt_unique_mandate_id',
+        ]);
+
+        $newPayment = $this->getNewMandatePaymentStub();
+        Cashier::$paymentModel::createFromMolliePayment($newPayment, $owner);
+
+        Event::fake();
+
+        $firstHandler = new FirstPaymentHandler($newPayment);
+        $firstOrder = $firstHandler->execute();
+
+        $secondHandler = new FirstPaymentHandler($newPayment);
+        $secondOrder = $secondHandler->execute();
+
+        $owner = $owner->fresh();
+
+        $this->assertFalse($firstHandler->wasAlreadyProcessed());
+        $this->assertTrue($secondHandler->wasAlreadyProcessed());
+        $this->assertTrue($firstOrder->is($secondOrder));
+        $this->assertTrue($owner->hasCredit());
+        $this->assertMoneyEURCents(100, $owner->credit('EUR')->money());
+        $this->assertEquals(1, $owner->orderItems()->count());
+        $this->assertEquals(1, $owner->orders()->count());
+        $this->assertEquals($firstOrder->id, Cashier::$paymentModel::first()->order_id);
+
+        Event::assertDispatched(MandateUpdated::class, 1);
+    }
+
     protected function getNewMandatePaymentStub(): Payment
     {
         $newPayment = new Payment(new MollieApiClient());