Purpose The purpose of this study was to compare clinical and radiographic outcomes of bipolar and monopolar radial head arthroplasty in treatment of radial head fracture at a mean follow-up of 6 years. Methods A retrospective multicentre cohort study of 30 patients treated for unreconstructable radial head fractures. Patients were treated either with a cemented bipolar or an uncemented monopolar radial head arthroplasty. All patients included were evaluated with patient-rated outcome questionnaire, physical examination, and radiographic evaluation at a mean of 6 years (range, 2-12 years) postoperatively. Results There was no statistical difference in QuickDASH between the bipolar or monopolar groups. The majority of patients had no to little pain during rest. Neither flexion nor extension of the injured arm was significantly affected by the type of prosthesis. None of the patients in the bipolar group had any secondary surgery at the time of follow-up. In the monopolar group, four patients required removal of the arthroplasty. Signs of ulnohumeral degenerative changes were seen in the majority of patients in both groups (55% in the monopolar group, 92% in the bipolar group). Conclusion In this retrospective cohort study comparing a bipolar and a monopolar radial head arthroplasty for treatment of radial head fractures, we found comparable functional outcome but more revision procedures in the monopolar group at a mean follow-up of 6 years.