There have been some difficulties in treatment of nonunion of the humeral shaft with osteoporosis. We report here the results on the treatment of nonunion with osteoporosis by using modified dual onlay graft method. The six cases among 34 nonunions of humeral shaft were operated by modified dual onlay graft. Initial treatments were applied one hanging arm cast, two plate fixations, three intramedullary nailings. In the 3 cases of them, we performed plate fixation and bone graft as secondary treatment. However, nonunion occurred with loosening of fixation. Modified dual anlay graft was applied from 6 to 36 months )average 12 months) after fracture of humerus. The proximal and distal humeral nonunion surface was made decorticated and flattened, and then reduction was performed. On the lateral side of nonunion site, 6 holes plate was fixed and on the medial side, fixed with 5~9 cm cortical bone which was harvested from proximal tibia. Cancellous bone graft was performed around nonunion area. Long arm splint was done for 2~4 weeks after operation. The union period was in the range of 3.5~6 months (average 4.9 months) in all six cases. Quicker bone union was achieved as the bone block got longer and the number of the fixation screw increased. We conclude that modified dual onlay graft method is the one of effective methods to treat nonunion of humeral shaft fracture with osteoporosis.