Yes, a dirty diaper can wake a baby up. When a baby is lying in their own waste for too long, it can be uncomfortable and cause them to become irritable or even cry. If a parent notices that the baby has had an accident in their diaper, they should take care of it immediately so the baby does not have to lay in it any longer than necessary. Even if the diaper change seems to wake up the sleeping infant, providing them with clean clothing will help ensure they are comfortable enough to drift back off into dreamland.