diff --git a/conntrackt/models.py b/conntrackt/models.py
--- a/conntrackt/models.py
+++ b/conntrackt/models.py
@@ -149,6 +149,26 @@ class Entity(models.Model):
 
         return reverse("entity", kwargs={'pk': self.pk})
 
+    def clean(self):
+        """
+        Performs additional validation checks on the submitted data. It will
+        verify the following:
+
+          - That entity is not linked to any other entity in case of project
+            change.
+        """
+
+        # Perform the check if entity is being updated.
+        if self.pk:
+            # Fetch the old data from database.
+            # @TODO: Is it better to do copying during __init__ instead?
+            old_object = Entity.objects.get(pk=1)
+
+            # Make sure that entity has no communications in current project if
+            # moving it around.
+            if self.project != old_object.project and (self.incoming_communications() or self.outgoing_communications()):
+                raise ValidationError("The entity cannot be moved to different project as long as it has valid communications with entities in current project.")
+
 
 class Interface(models.Model):
     """