Background and purpose — Humeral shaft fractures (HSF) can be treated surgically or non-surgically. National trends and distributions are sparsely reported. We present the temporal trends in epidemiology of adult HSF in Denmark, with the primary aim of reporting HSF incidences, and the secondary aim of reporting on the primary treatment man-agement. Patients and methods — The diagnosis (International Classification of Diseases Version 10 [ICD-10]: S42.3) and surgical procedure codes for HSF were obtained from the Danish National Patient Registry (DNPR) covering 1996– 2018. The diagnosis code for HSF is validated in the DNPR with a positive predictive value of 89%. Patients aged 18 years and above were included. Surgical treatment was defined as a diagnosis of HSF combined with a surgical procedure within 3 weeks of injury. Cases without relevant registered procedures within 3 weeks were defined as nonsurgical treatment cases. Results — 23,718 HSF (62% female) were identified in the DNPR. The overall mean incidence was 25/100,000/ year and was stable over 23 years. The population above 50 years accounted for 78% of all HSF. Non-surgical treatment accounted for 87% of treatments and was stable during the study period. Temporal changes were observed regarding surgical procedures; intramedullary nailing decreased from 57% to 26% and plate osteosynthesis increased from 12% to 69%. Conclusion — The overall incidence for HSF remained stable from 1996 to 2018. Most cases were females aged 50 years and above. The preferred primary treatment for HSF was non-surgical for all ages. Plate osteosynthesis became more popular than intramedullary nailing over the study period.