Masseter muscle hypertrophy also known as Benign Masseteric hypertrophy (BMH) or Idiopathic Masseteric Muscle Hypertrophy (IMMH) is a rare condition of unknown cause and can occur unilaterally or bilaterally. Pain may be a symptom, but most frequently patient approaches, to the clinician for cosmetic reasons. In majority of the cases the etiological factor is unknown therefore it is considered to be idiopathic. It is most commonly bilateral, and rarely unilateral in occurrence. The purpose of this article is to report a case of acquired idiopathic unilateral masseter hypertrophy in a 23 year old female, diagnosed using a detailed history, intra oral, extra oral examination and imaging modalities and was surgically treated by debulking of masseter muscle and mandible ramus osteotomy.