diff --git a/mailpoet/lib/Automation/Integrations/MailPoet/Hooks/CreateAutomationRunHook.php b/mailpoet/lib/Automation/Integrations/MailPoet/Hooks/CreateAutomationRunHook.php
index bd218042d2..fb6d6b974f 100644
--- a/mailpoet/lib/Automation/Integrations/MailPoet/Hooks/CreateAutomationRunHook.php
+++ b/mailpoet/lib/Automation/Integrations/MailPoet/Hooks/CreateAutomationRunHook.php
@@ -5,23 +5,20 @@ namespace MailPoet\Automation\Integrations\MailPoet\Hooks;
 use MailPoet\Automation\Engine\Data\StepRunArgs;
 use MailPoet\Automation\Engine\Hooks;
 use MailPoet\Automation\Engine\Storage\AutomationRunStorage;
-use MailPoet\Automation\Engine\WordPress;
 use MailPoet\Automation\Integrations\MailPoet\Subjects\SubscriberSubject;
+use MailPoet\Util\Security;
+use MailPoet\WP\Functions as WPFunctions;
 
 class CreateAutomationRunHook {
-
-
-  /** @var WordPress */
-  private $wp;
-
-  private $automationRunStorage;
+  private AutomationRunStorage $automationRunStorage;
+  private WPFunctions $wp;
 
   public function __construct(
-    WordPress $wp,
-    AutomationRunStorage $automationRunStorage
+    AutomationRunStorage $automationRunStorage,
+    WPFunctions $wp
   ) {
-    $this->wp = $wp;
     $this->automationRunStorage = $automationRunStorage;
+    $this->wp = $wp;
   }
 
   public function init(): void {
@@ -39,11 +36,29 @@ class CreateAutomationRunHook {
       return true;
     }
 
-    $subscriberSubject = $args->getAutomationRun()->getSubjects(SubscriberSubject::KEY);
+    $subscriberSubject = array_values($args->getAutomationRun()->getSubjects(SubscriberSubject::KEY))[0] ?? null;
     if (!$subscriberSubject) {
       return true;
     }
 
-    return $this->automationRunStorage->getCountByAutomationAndSubject($automation, current($subscriberSubject)) === 0;
+    // Use locking mechanism to minimize the risk of race conditions.
+    // WP transients don't provide atomic operations, so we can't guarantee
+    // race-condition safety with a 100% certainty, but we can significantly
+    // minimize the risk by generating and re-checking a unique lock value.
+    $key = sprintf('mailpoet:run-once-per-subscriber:[%s][%s]', $automation->getId(), $subscriberSubject->getHash());
+
+    // 1. If lock already exists, do not create automation run.
+    $value = $this->wp->getTransient($key);
+    if ($value) {
+      return false;
+    }
+
+    // 2. If lock does not exist, create it with a unique value.
+    $value = Security::generateRandomString(16);
+    $this->wp->setTransient($key, $value, MINUTE_IN_SECONDS);
+
+    // 3. If no automation run exist, ensure that the lock wasn't updated by another process.
+    $count = $this->automationRunStorage->getCountByAutomationAndSubject($automation, $subscriberSubject);
+    return $count === 0 && $this->wp->getTransient($key) === $value;
   }
 }