Closed flexor tendon ruptures due to trauma without external wound are rare. When the flexor tendon has excessive loading, failure occurs at the tendon insertion or its origin from the bone. It is likely to result in avulsion fracture rather than rupture of the proper portion of the tendon by forceful grasping with hyperextension. However, we have experienced three cases of closed flexor tendon ruptures at zone V, caused by forceful grasping or hyperextension mechanism against resistance. On physical examination, these patients could not flex interphalangeal joint of thumb or distal interphalangeal joint of the fifth finger. All patients underwent MRI or ultrasonography to find out the location of loss in continuity of the flexor tendons before the operation. After identifying the location, flexor tendon repair or tendon graft using palmaris longus were performed.