diff --git a/taiga/projects/serializers.py b/taiga/projects/serializers.py
index 09b54aea..43517474 100644
--- a/taiga/projects/serializers.py
+++ b/taiga/projects/serializers.py
@@ -99,6 +99,11 @@ class ProjectSerializer(serializers.ModelSerializer):
         # The "stars_count" attribute is attached in the get_queryset of the viewset.
         return getattr(obj, "stars_count", 0)
 
+    def validate_slug(self, attrs, source):
+        project_with_slug = models.Project.objects.filter(slug=attrs[source])
+        if source == "slug" and project_with_slug.exists():
+            raise serializers.ValidationError(_("Slug duplicated for the project"))
+
 
 class ProjectDetailSerializer(ProjectSerializer):
     roles = serializers.SerializerMethodField("get_list_of_roles")