A 15-year-old pitcher on a boys' Little League baseball team suffered spontaneous rupture of the extensor pollicis brevis (EPB) tendon. Since the EPB tendon was, at surgery, found hypoplastic and non-functional, transfer of the extensor indicis proprius (EIP) tendon was carried out. After a 6-month period of rehabilitation and follow-up, the patient was able to resume playing baseball. Although rupture of the EPB is rare, transfer of the EIP tendon is one of the treatments of choice for such injuries.