Plexiform neurofibroma is generally considered as a component of neurofibromatosis 1, and a great majority of the cases with plexiform neurofibroma display other symptoms related to neurofibromatosis. Plexiform neurofibromas occur frequently in the head and neck region due to the rich innervation of the area, however appear rarely in the extremities. We report here an isolated giant plexiform neurofibroma involving the common peroneal nerve branches without symptoms related to neurofibromatosis in a 5-year-old case. Surgical excision was performed due to pain and numbness in the leg, and against the possibility of malignant transformation due to sudden growth observed in the tumor. One month following the excision of all the reachable tumoral tissues, tendon transfer surgery was performed for the ankle and toe extensions. Our case stands as the only reported case of isolated giant plexiform neurofibroma involving the common peroneal nerve in the pediatric age.