Duplication of the thumb is the most common polydactyly of the hand. Wassel's classification is frequently used to classify the polydactyly of the hand. His classification was based on the level of duplication and the number of bones in the thumb, and has seven groups (Types I-VII) according to the level of the bifurcation, except for his Type VII. The most common type is the bifurcation at the metacarpophalangeal joint (Type IV). In this paper, we report a very rare case of Type V thumb polydactyly in a 42-year-old man, who presented with swan neck deformity of the radial thumb and discuss the plain radiography and computed tomography (CT) findings. Kumar recently reported plain radiography findings in a case of bifid first metacarpal in a 13-year-old girl, who presented with swan neck deformity of the left thumb. To our knowledge, our case is the second presented case that has a swan neck deformity with bifid metacarpal.