diff --git a/src/State/WorkflowDeleteProcessor.php b/src/State/WorkflowDeleteProcessor.php
new file mode 100644
index 0000000..a0efec9
--- /dev/null
+++ b/src/State/WorkflowDeleteProcessor.php
@@ -0,0 +1,42 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\State;
+
+use ApiPlatform\Metadata\Operation;
+use ApiPlatform\State\ProcessorInterface;
+use App\Entity\Workflow;
+use Doctrine\ORM\EntityManagerInterface;
+use Symfony\Component\HttpKernel\Exception\HttpException;
+
+/**
+ * @implements ProcessorInterface<Workflow, void>
+ */
+final readonly class WorkflowDeleteProcessor implements ProcessorInterface
+{
+    public function __construct(
+        private EntityManagerInterface $entityManager,
+    ) {}
+
+    public function process(mixed $data, Operation $operation, array $uriVariables = [], array $context = []): void
+    {
+        /** @var Workflow $workflow */
+        $workflow = $data;
+
+        $count = (int) $this->entityManager->getConnection()->fetchOne(
+            'SELECT COUNT(*) FROM project WHERE workflow_id = :id',
+            ['id' => $workflow->getId()],
+        );
+
+        if ($count > 0) {
+            throw new HttpException(409, sprintf(
+                'Workflow used by %d project(s). Reassign them before deleting.',
+                $count,
+            ));
+        }
+
+        $this->entityManager->remove($workflow);
+        $this->entityManager->flush();
+    }
+}