A 6-year-old otherwise healthy girl presented with a Wassel VI duplication of the left thumb metacarpal and triphalangeal radial and ulnar thumbs. The patient underwent successful thumb reconstruction by transposition of the distal ulnar thumb onto the radial thumb metacarpal. To the best of our knowledge, this case report represents the first published anatomical dissection and surgical reconstruction of a Wassel VI duplication with triphalangeal radial and ulnar thumbs.