Mental Health First Aid (MHFA) is a standardized, psychoeducational programme developed to empower the public to approach, support and refer individuals in distress by improving course participants' knowledge, attitudes and behaviours related to mental ill-health. The present paper aims to synthesize published evaluations of the MHFA programme in a meta-analysis to estimate its effects and potential as a public mental health awareness-increasing strategy. Fifteen relevant papers were identified through a systematic literature search. Standardized effect sizes were calculated for three different outcome measures: change in knowledge, attitudes, and helping behaviours. The results of the meta-analysis for these outcomes yielded a mean effect size of Glass's Δ = 0.56 (95% CI = 0.38 - 0.74; p < 0.001), 0.28 (95% CI = 0.22 - 0.35; p < 0.001) and 0.25 (95% CI = 0.12 - 0.38; p < 0.001), respectively. Results were homogenous, and moderator analyses suggested no systematic bias or differences in results related to study design (with or without control group) or 'publication quality' (journal impact factor). The results demonstrate that MHFA increases participants' knowledge regarding mental health, decreases their negative attitudes, and increases supportive behaviours toward individuals with mental health problems. The MHFA programme appears recommendable for public health action.