A ganglion is the most common soft tissue tumor. But an intratendinous ganglion is a rare lesion of unknown etiology but with a natural history that originates within the tendon. A 52 year-old man complained of a palpable, non-tender mass in the dorsum of the right foot. We present a case of an intratendinous ganglion that developed in the extensor hallucis brevis tendon and which was treated successfully by excision.