Postoperative periprosthetic fracture of the femur after hip arthroplasty is a serious complication that can be difficult to treat. Moreover, it has become more common in recent years, as the cases of hip arthroplasty and revisonal hip arthroplasty increase. We have experienced a postoperative periprosthetic fracture of th femur probably caused by a surgical instrument left in the medullary canal during hip arthroplasty. We report this case with reference to other related articles.