The aim of this study was to determine the prevalence of burnout in mental health nurses and to identify its predictors. A systematic review was conducted of studies published in the following databases: CINAHL, Dialnet, LILACS, ProQuest, PsycINFO, PubMed, SciELO, and Scopus. The search equation used was “Nurs * AND Burnout AND mental health”. Subsequently, three fixed‐effects meta‐analyses were performed, one for each dimension of burnout, to calculate its prevalence and the corresponding confidence intervals. The data were analysed using StatsDirect meta‐analysis software. Eleven studies were finally included (n = 11). In most cases, the literature informs about moderate levels of emotional exhaustion, depersonalization, and personal accomplishment. The studies inform that variables such as work overload, work‐related stress, professional seniority, male gender, being single, and aggression at work, among other factors, contribute to burnout development. The meta‐analytic prevalence estimations of burnout with a sample of n = 868 mental health nurses are 25% for high emotional exhaustion, 15% for depersonalization, and 22% for low personal accomplishment. From a workforce development and safety perspective, it is important for managers to address the emotional exhaustion and low personal accomplishment aspects of burnout reported in the workplace by mental health nurses.