Treatment of recurrent ulnar nonunion with moderate bone defects in the presence of inadequate vascularity of surrounding tissues requires a vascularized bone graft (VBG). We report a case of recurrent ulnar nonunion that was treated successfully with a radius graft pedicled on the anterior interosseous artery (AIA) branches. A 48-year-old female presented with recurrent ulnar nonunion following ulnar shortening osteotomy with 5-mm bone defects at 5 cm proximal to the wrist. We elevated the VBG with a 2, 3 intercompartmental supraretinacular artery and 4th extensor compartmental artery, and gently inserted the VBG into the recipient site, enabling stable osteosynthesis. X-ray imaging revealed consolidation after 4 months without restriction of the range of motion of the wrist or extensor paralysis. As the recipient site was located in the proximal area, none of the posterior interosseous nerve motor branches were sacrificed to elevate the VBG with AIA branches. Anatomical information regarding the vascular pattern of the AIA and its relation to posterior interosseous nerves provides reliable solutions for recurrent ulnar nonunion through a distal radius graft pedicled on AIA branches.