Long-term subjective and objective outcomes of 24 tendon interposition arthroplasties in 17 patients and 32 trapeziometacarpal (TMC) arthrodeses in 26 patients were compared retrospectively in a standardized manner. Tendon interposition arthroplasty led to complications less often (27%) than TMC arthrodesis (39%). Patients in the tendon interposition arthroplasty group reported significantly less pain, less temperature intolerance, and better thumb mobility and were more satisfied with pain symptoms than patients in the arthrodesis group. Patients undergoing tendon interposition arthroplasty had better thumb opposition, interphalangeal joint mobility, and radial and palmar TMC joint range of motion. No statistically significant differences were found in tip pinch, key pinch, and grip strength between the 2 groups. Proximal first metacarpal collapse occurred in the tendon interposition patients without affecting subjective or objective outcome. Seven of 25 patients with TMC arthrodesis had pseudarthrosis. Tendon interposition arthroplasty seems to be preferable to TMC joint arthrodesis for the treatment of TMC arthritis.