Giant cell tumor of the tendon sheath(GCTTS) is a family of lesions usually involving the joint synovia, bursae and tendon sheath. Localized forms mainly involve the fingers and hands. GCTTS may occur at any age, but it is most common between the ages of 30 and 50 years. GCTTS is firm in consistency and measures from 1 to 3 cm in diameter. A 51-year-old male presented to the dermatology with a painless, firm skin colored mass on the radial aspect of distal phalanx of the left index finger. The lesion was asymptomatic, about 1.5 x 2 cm, sized skin colored, firm tumor. Microscopically, the tumor located in dermis was encapsulated and showed highly cellular proliferation within a distinctly hyalinized collagenous stroma. In cellular area, most cells were numerous histiocyte-like cells with kidney-shaped, oval neuclei and abundant eosinophilic cytoplasm. Some osteoclast-like multinucleated giant cells were also distributed in the cellular area. Smooth muscle actin stain was negative. Finally, the diagnosis of GCTTS was made on the basis of the histologic findings. He was transferred to orthopedic surgery department and underwent excision of the lesion. The histopathology result of excised specimen was also consistent with GCTTS. Our case was typical for the clinical characteristic of GCTTS. Korean reported cases are currently seven in the dermatologic literature. We report a rare case that suggests GCTTS clinically and histologically.