The iliac crest is a common donor site for autogenous bone graft as it offers the advantage of easy access and a relatively large and safe supply of bone. One of the less frequently reported complications of harvesting bone grafts from the iliac crest is a graft-site hernia. In the last decade less than 15 cases have been reported, however the true incidence of this complication is unknown. We report a case of iliac crest bone graft hernia in an obese diabetic female. The significant feature of this case was a large swelling six weeks postoperatively that was thought to be a hematoma. The actual diagnosis of hernia was made on the operating table during an attempt to evacuate the hematoma. Hence a high degree of suspicion is needed to diagnose a hernia following an iliac crest bone graft, particularly in obese patients and the suspicion should lead to confirmation by a CT scan.