BACKGROUND The aim of this study was to evaluate the clinical and radiological results of adult forearm fractures treated with interlocking intramedullary nailing. METHODS This retrospective study included 21 patients who were treated with intramedullary interlocking nailing for forearm fractures between January 2010 and September 2017. All patients were treated with intramedullary forearm nails designed to allow interfragmentary compression. The medical records and radiographs of all patients were evaluated. Fractures were classified according to the AO/OTA classification system by analyzing the radiographs. Union time, union rate, clinical outcome, and complications were evaluated. RESULTS Primary intramedullary osteosynthesis was performed in 17 patients with forearm shaft fractures. The average union time was 10 weeks (range, 8-16 weeks) in the primary osteosynthesis cohort. Secondary intramedullary osteosynthesis was performed in four patients following the removal of plates and screws due to nonunions. For this group of patients, bone union took an average of 17 weeks (range 8-24 weeks). The overall union rate was 95.24% in the 21 forearm fractures which were treated with an intramedullary interlocking nail with a compression screw that allows interfragmentary compression to be obtained. Overall complications included one nonunion, one postoperative rupture of the extensor pollicis longus tendon, and 1 postoperative transitory radial nerve palsy. CONCLUSIONS Intramedullary interlocking nailing with a compression screw is an alternative method of fixation for treating adult forearm fractures and provides good clinical outcomes with reliable union rates.