The superficial peroneal nerve presents great anatomic variability regarding its emergence from the crural fascia, course, branching pattern, and distribution area. Entrapment neuropathy of the superficial peroneal nerve has been documented in the published data, resulting in pain and paresthesia over the dorsum of the foot. We report a case of a female cadaver in which an accessory superficial peroneal sensory nerve was encountered. The nerve originated from the main superficial peroneal nerve trunk, proximal to the superficial peroneal nerve emergence from the crural fascia, and followed a subfascial course. After fascial penetration, the supernumerary nerve was distributed to the skin of the proximal dorsum of the foot and lateral malleolar area. A potential entrapment site of the nerve was observed at the lateral malleolar area, because the accessory nerve traveled through a fascial tunnel while perforating the crural fascia, and presented with distinct post-stenotic enlargement at its exit point. The likely presence of such a very rare variant and its potential entrapment is essential for the physician and surgeon to establish a correct diagnosis and avoid complications during procedures to the foot and ankle region.