Osteochondroma is one of the most common benign bone tumors. It is easy for dermatologists to misdiagnose osteochondroma on the fingers or toes as other cutaneous tumors including pilomatricoma, epidermal cyst, and glomus tumor. We report a case of a 42-year-old woman presenting with a palpable mass on the left thumb. Skin biopsy was performed in the other hospital a year ago and she heard the result as a viral wart. In our hospital, the tumor was checked by X-ray, which showed a calcified nodule on the distal phalanx. Bizarre parosteal osteochondromatosis proliferation was suspected on MRI but bony connection between a bony spur and the distal phalanx was obscure. We additionally performed a computed tomography, which revealed a 5mm-sized bony spur connected with cortical bone. Specimen after orthopedic surgery showed fibrous tissue and cartilage cap composed of hyaline cartilage. Based on these findings, we concluded her tumor is an osteochondroma masquerading as viral wart.