Rupture of the tibialis posterior tendon may occur during a trauma in pronation-external rotation of the foot or, less commonly, during a direct trauma of the ankle. When an isolated fracture of the medial malleolus is present, it is more likely that a direct trauma has occurred. A 36-year-old man with a non-displaced medial malleolar fracture was evaluated. Repair of the tendon and reduction of the fracture were performed. Twenty-four months after the operation, the fracture was completely healed, the patient was asymptomatic, he had a normal ankle range of motion, and the function and strength of the tibialis posterior tendon were equal to those on the contralateral side. Early surgical repair of the tibialis posterior tendon combined with malleolar fracture reduction is recommended to avoid progression to a plano-valgus foot.