A five-year-old male boxer, previously diagnosed with leishmaniasis and hypothyroidism, had gradually become unable to bear weight on its left hindlimb. Physical examination revealed a left popliteal lymphadenopathy, mild crepitus, and severe swelling of the left tarsal joint, a radiographic examination of which revealed severe bone destruction of the talus and a periosteal reaction of the calcaneus. Laboratory findings and serological tests suggested an active leishmanial infection, and a Leishmania species was identified by direct cytology of a sample from the osteolytic area and by indirect immunohistochemistry of a bone biopsy. The dog's condition improved when it was treated with meglumine antimonate and allopurinol. Because of the large osteolytic area and the increased use of the affected leg, a partial tarsal arthrodesis was performed to prevent a fracture. Five months after the surgery, the osteolytic area had healed completely and the calcaneus periosteal reaction had disappeared.