A tibialis posterior tendon rupture associated with a closed ankle fracture occured in a 23-yearold man. The tendon rupture was not diagnosed before surgery but was recognized at the time of open reduction. The treatment was open reduction and internal fixation of the ankle fracture with primary repair of the tendon. One year postoperatively, he had a nearly full range of ankle motion without pain and a nonmal longitudinal arch. This tendon injury, although rare, should be considered in the management of ankle fracture because the tendon rupture could easily have been overlooked.