Aim: To assess the metabolic effects of dopamine agonists compared with placebo in randomized controlled trials (RCTs) including adults with type 2 diabetes. Materials and methods: Eligible trials were identified by searching PubMed, Embase and CENTRAL. The primary outcomes were HbA1c and serious adverse events (SAEs) assessed at longest available follow-up. Secondary outcomes were fasting plasma glucose, adverse events, body weight, hypoglycaemia and triglycerides. We assessed risk of bias and evaluated the certainty of the evidence with the Grading of Recommendations Assessment, Development and Evaluation (GRADE). Results: Nine RCTs enrolling 3456 participants were included, six of which assessed the effect of bromocriptine, and the other three the effect of cabergoline. Dopamine agonists reduced HbA1c with 0.69 standardized mean difference (95% CI = 0.28 to 1.09; P =.0008; I² = 80%; GRADE: low) compared with placebo. There was no difference in the effect between bromocriptine and cabergoline. Heterogeneity was partly explained by dosage and study duration, both of which were inversely associated with effect size. Only one large trial reported SAEs and no difference was reported for the risk of an SAE (RR = 0.89; 95% CI = 0.70 to 1.12; P =.32) between active intervention and placebo. Secondary outcomes suggested a decrease in fasting plasma glucose and triglycerides and no effect on the remaining outcomes. Conclusion: Dopamine agonists reduce HbA1c as well as fasting plasma glucose and triglycerides in patients with type 2 diabetes without causing SAEs. These data are based on moderate to low quality evidence thus our confidence in the effect estimates is limited.