A 79-year-old man presented with a painless, soft, subcutaneous mass lesion of the right volar wrist that had been slowly growing for 3 years. A cloudy, yellow serous effusion was aspirated from the punctured mass, from which Phaeoacremonium spp., an extremely rare cause of tenosynovitis, was isolated in culture. Total synovectomy was performed without the use of antifungal agents. No recurrence or complications occurred as of 6 months after surgery. Fungal infection is rare but should be considered in the differentiation of chronic tenosynovitis.