We performed endoscopic bone grafting for eight patients of delayed union and nonunion which developed after femoral and humeral shaft fractures. The mean interval from initial intervention to endoscopic bone grafting was 7.3 months. Six patients of delayed union and nonunion healed at 4.1 months on average. Two patients had unsatisfactory healing and eventually underwent non-endoscopic revisional surgery. There was no intraoperative on postoperative complication. Endoscopic bone grafting can be a less invasive alternative, obtaining rapid bone union in cases of compromised healing of the diaphyseal fracture.