We report an unusual case of Kirschner wire migration from the proximal humerus into the thoracic cavity and diaphragm which induced pneumothorax and hemoperitoneum. An 81-year-old woman admitted to the emergency room due to sudden onset of dyspnea. X-rays showed pneumothorax and old proximal humerus fracture fixed with rush pins and K-wires. One of K-wires was seen on the diaphragm level at posterior gutter of chest wall. Through the abdomen, K-wire was removed from the diaphragm and a chest tube was inserted. The potential for K-wires to migrate must be recognized, and frequent postoperative radiographic studies have to be performed for the early detection of loosening and migration. It appears that if K-wires are used for fixation of proximal humerus, the lateral ends must be bent to prevent medial migration, and when the desired therapeutic goals have been achieved, these pins have to be susbsequently removed as soon as possible.