Myasthenia Gravis (MG) is characterized clinically by weakness of the skeletal muscle and fatigability on exertion. Frequently, patients will initially present with an ocular symptom of ptosis, diplopia or both. On rare occasions, patients may present to the dentist with a peculiar complaint. We report a patient who complained of a ‘heavy and dropping’ jaw. He was unable to occlude or masticate, making him resort to manually moving his lower jaw during meal times. This condition usually worsened as the day progressed. Upon further evaluation, MG was confirmed. With treatment, the patient was able to occlude and achieved maximum intercuspation without any guidance. This case report discusses a case of newly diagnosed MG that presented with a rare and uncommon complaint of a weak mandible with inability to masticate. We have highlighted specific clinical features of MG to allow prompt recognition as well as discussion on dental management of such patient when presenting to a dentist.