Tarsal tunnel syndrome is relatively an uncommon and usually under-recognized or misdiagnosed condition. We report a case of posterior tarsal tunnel syndrome caused by a ganglion . A 58-year-old woman complained of burning and tingling sensation along the left sole and presented weakness, muscle atrophy, and Tinel's sign in the left foot. Electrodiagnostic study revealed prolonged terminal latency, reduced compound muscle action potential, absent sensory nelve potential, and denervation potentials. After removal of the ganglion, patient's symptoms improved and the electrodiagnostic study performed after two months showed significant improvement.