Developmental malformations of the teeth might result in alterations of their size, shape, and structure. An accessory cusp is a developmental alteration to the shape of the teeth and is more commonly found in anterior teeth, and its occurrence in permanent molars is quite rare. Accessory cusps occurring in permanent mandibular molars are termed as protostylids. Although they do not pose any significant problem with respect to the function and occlusion, it is of tremendous importance in forensic odontology. This case report presents a rare finding of protostylid on the permanent mandibular molar, and its clinical implications are illustrated.