The literature contains numerous accounts of the muscular anatomy of the medial pterygoid muscle, but little is known about the detailed vascular supply of the muscle. Numerous surgical procedures, such as mandibular ramus osteotomy, angle reduction, and/or parotidectomy, are performed around the muscle in the absence of this information. This study aimed to clarify the arterial supplies to the medial pterygoid muscle to provide critical information for use during various surgical procedures. Detailed dissections were performed on 20 sides of adult cadaveric head and neck specimens after injecting the carotid artery with red liquid neoprene latex. The medial pterygoid muscle was supplied by the following 5 branches of the external carotid artery: (1) the pterygoid artery of the maxillary artery, (2) a direct muscular branch of the facial artery, (3) the ascending palatine artery, (4) an anterior muscular branch of the facial artery, and (5) a previously undescribed muscular branch of the external carotid artery. This analysis of vascular anatomy has revealed new anatomic information on the blood supplies to the medial pterygoid muscle and will be useful to the development of guidelines for preventing hemorrhage during surgical procedures