Peroneal nerve injury in the lateral aspect of the knee is frequent, commonly dominated by traumatic or compressive etiologies. Tumors, generally synovial cysts, are exceptional causes. We report a case of a 70-year-old women referred for assessment of peroneal palsy syndrome found to be related to peroneal schwannoma in the lateral aspect of the knee. Schwannoma is the most frequent peripheral nerve benign tumor. It is commonly limited to cranial and upper limb nerves. Localization on the lower limbs (sciatic nerve) has been reported in 1 percent of cases. The peroneal nerve localizaton has not been reported to date. We underline difficulties of diagnosis inherent to this particular localization.