Objective. To synthesize the literature on the efficacy of existing nonsurgical interventions for trapeziometacarpal (TM) osteoarthritis (TMO). Methods. A medical librarian conducted an electronic search in 16 databases. Two authors independently carried out study selection, data extraction, and risk-of-bias assessment. The Agency for Healthcare Research and Quality guidance was followed to integrate a valid body of evidence from the existing systematic reviews. Intervention effects were estimated based on the Cochrane Collaboration review methodology. Results. We identified 17 systematic reviews, 34 randomized controlled trials, and 6 nonrandomized controlled trials. Most of the studies had unclear or high risk of biases. Evidence of low-to-moderate quality supports the superiority of the following interventions for pain and/or physical function: 1) saline over steroid intraarticular injections confirmed by radiography, 2) saline injections over sham (i.e., pressure) in tender subcutaneous areas, 3) custommade thermoplastic thumb orthosis over no intervention or a control, 4) custom-made thermoplastic hand-based TM joint orthosis over no intervention, 5) radial nerve mobilization over sham ultrasound, and 6) a combination of hand exercises and TM joint and median/radial nerve mobilization over sham ultrasound. Conclusion. This comprehensive systematic review allowed collating evidence-based data on the efficacy of nonsurgical interventions for TMO. Steroid intraarticular injections would not be more effective than saline injections. Rehabilitative interventions (orthosis, exercises, nerve mobilization) would be efficacious. However, these findings must be treated with circumspection due to methodologic limitations in many studies.