This study was conducted to assess a stepwise surgical procedure applied to treat a continuous series of patients with aseptic atrophic nonunion of long bones. A retrospective review was performed of the medical files of patients treated by the senior author between January 2014 and January 2021 for aseptic atrophic nonunion of long bones using a standard stepwise surgical procedure consisting of four successive surgical steps: bridge locked plating, aggressive osteoperiosteal decortication, copious autologous iliac bone grafting, and tight closure without drainage. Patients were clinically and radiographically evaluated until bone healing, then at final follow-up for the purpose of the study. The primary objective of the study was to assess completion of bone healing; secondary objectives were the time required reaching bone union, the occurrence of complications at the iliac bone graft donor site, and the achievement of bone consolidation after a second attempt of treatment when indicated following failure of the index procedure. There were a total of 55 patients. One patient died from myocardial infarction before reaching bone healing and another one lost from early follow-up. There were remaining 53 patients with 37years of mean age. The affected bone was the clavicle in five patients, humerus in 14, ulna in four, radius in one, femur in 13, and tibia in 16. The mean follow-up period was 3.4years. A total of 52 patients (98.1%) achieved bone healing at a mean of 14.8weeks from the index procedure. The only patient who did not reach bone healing after the index procedure was successfully revised using decortication-bone graft and new fixation with intra-medullary femoral nailing. Four patients (7.5%) developed local complications at the site of iliac bone harvesting. Our stepwise surgical procedure was very effective treating aseptic atrophic nonunion of long bones. However, as this study is a retrospective review of a limited series of one surgeon's experience, prospective comparative studies with large number of patients are suitable to define the advantages and indications of the procedure herein described.