The use of an intramedullary nail in the treatment of humeral non-unions remains controversial. This study evaluated the treatment of humeral delayed and non-unions with reamed nailing and compression. In a retrospective analysis of prospectively gathered data from 26 cases all treated with the Telescopic Locking Nail (TLN), the healing rate after the first intervention for non-union was 58%. After one or more re-interventions combined with an external cancellous bone graft at some time during follow-up, 90% of the 21 patients with complete follow-up eventually healed after a mean of 22 months. A total of 49 procedures with a mean of 1.9 per patient were needed. After a mean follow-up of 65 (range 24-88) months, we conducted a study to assess the functional results in the shoulder and elbow. Twelve patients were suitable for inclusion. We used the Neer and Morrey score for shoulder and elbow function, respectively. For the Neer score the median was 91 points and for the Morrey score 94 points. The outcome suggests that simple reamed nailing of humeral non-union is insufficient. Reamed interlocked nailing is feasible, provided that the primary intervention for non-union is combined with an external cancellous bone graft.