Introduction: Both joint mobilisation and immobilisation are thought to be effective in the treatment of first carpo metacarpal joint (CMCJ) osteoarthritis (OA). The objective of this review was to establish whether either intervention reduced pain and improved pinch strength in people with first CMCJ OA in the short term and assess whether one intervention is superior to the other. Method: This was a systematic review and meta-analysis. Seven databases were searched until May 2021. Only RCTs were included. The Cochrane Risk of Bias Tool and the Grade of Recommendations Assessment, Development and Evaluation system were utilised to rate the evidence. Random-effects meta-analysis with subgroup analyses were used. Results: Eight studies were included with a total of 417 participants. Mobilisation treatments included manual therapy with or without exercise while immobilisation interventions utilised thumb splinting with several different designs. Very low quality and low-quality evidence showed that mobilisation led to statistically but not clinically significant improvements in pain (standardised mean difference (SMD) = 0.53; 95% confidence interval (CI) = 0.03 to 1; I2 = 60%; p = 0.06) and pinch strength (SMD = 0.35; 95% CI = 0.03 to 0.7; I2 = 12%; p = 0.3) compared to placebo. Very low-quality and low-quality evidence showed no effect on pain and pinch strength compared to a control or no intervention. Subgroup analyses revealed no difference between interventions. Discussion: Neither mobilisation nor immobilisation alone led to clinically important improvements in pain or pinch strength in the short term in people with symptomatic first CMCJ OA. Neither therapeutic strategy appeared to be superior.