Accessible summaryWhat is known on the subject? Laughter yoga is claimed to promote mental health and has become increasingly popular worldwide. There has been no systematic review of laughter yoga intervention studies and thus evidence of its effects on mental health is unclear. What the paper adds to existing knowledge? Laughter Yoga interventions improved depressive symptoms in two studies over the short term. There is a lack of good quality evidence to show that laughter yoga is more effective than other group‐based interventions in improving mental health. What are the implications for practice? Well‐conducted and clearly reported trials of laughter yoga are needed before the intervention can be considered as an evidence‐based intervention to improve mental health. AbstractIntroductionLaughter Yoga is claimed to promote mental health and is increasingly popular worldwide. Despite its popularity, there has been no systematic review of Laughter Yoga intervention studies and thus evidence of its effects on mental health is unclear.AimThis review aimed to critically evaluate the effects of group‐based Laughter Yoga on improving mental health in adults.MethodWe conducted a systematic review of experimental studies (published from 1995 to 2017). Study quality was assessed, the effect sizes for individual mental health outcomes were calculated and all reviewed studies were narratively synthesized.ResultsSix experimental studies with inconsistent results were included in this review. The most promising effect of Laughter Yoga is the improvement of depressive symptoms, indicating significant medium‐large effect sizes in two studies over the short term. The overall level of evidence was weak due to poor study quality and risks of bias.DiscussionLaughter Yoga shows potential, but currently there is insufficient evidence to support its effectiveness in improving mental health when compared to other group‐based interventions.Implications for practiceThis review highlights the need to conduct rigorous trials of laughter yoga before the intervention can be considered as an evidence‐based intervention to improve mental health.