Infertility and poor breeding performance are frequently encountered in avicultural facilities. The problems of infertility or inadequate performance may have either medical or nonmedical origins. It is not always possible to diagnose causes of infertility with the noninvasive diagnostic methods that are used routinely. Testicular biopsy can be used as a possible diagnostic tool to confirm infertility in male birds. A variety of psittacine birds (n = 39) were anesthetized and a testicular biopsy was performed endoscopically using a right or left lateral approach caudal to the femur. The technique and postoperative complications are reviewed.