Ossification of the Achilles tendon is a rare clinical condition characterized by the presence of one or more segments of variable sized ossified mass within the tendon. The cause of the condition is obscure. We present the case of a 41 year-old male patient with pain in the Achilles tendon due to bilateral ossification of the tendon near the calcaneus insertion. The case was evaluated by ultrasonography, single photon emission computed tomography, and transmission computed tomography. In this case, we regarded repetitive microtrauma as the cause of the ossification based on the bilateral occurrence.