Acromial fractures are rare but severe complications which can occur during subacromial decompression. We report a case of acromial pseudarthrosis which was discovered belatedly due to persistent pain after several operations. The pseudarthrosis was successfully treated by osteosynthesis with a distal radius plate and implantation of a monocortical bone graft from the iliac crest. Two years after surgery, the fracture has healed and the patient's pain improved significantly. In the constant score the patient achieved postoperatively 58 points compared to 25 points before surgery and 65 points compared to 25 points preoperatively in the subjective shoulder rating system (SSRS). Postoperatively, the patient had a better range of motion with active abduction/adduction of 50/0/25º (30/0/20° preoperatively), outward rotation/inward rotation of 35/0/45º (30/0/30° preoperatively) and anteversion/retroversion of 60/0/35° (35/0/20° preoperatively).