Summary. Background. In England, psychosis incidence is 31.7×100,000 persons per year. Mindfulness-based interventions for psychosis (MBIp) might reduce its symptoms; however, the research outcomes on its effect size (ES) vary considerably. This project aims to ascertain the existing evidence. Methods. Eight publications from a pool of over 260 studies were extracted and analysed at meta-analysis for ES as satisfying the inclusion criteria. Results. MBIp has a moderate ES (r=0.34; p<.001) on psychosis with a 95% confidence interval (CI) of 0.26-0.42 (small to high). Discussion. MBIp improves psychosis symptoms. However, the studies analysed show heterogeneity in ES. Hence only conditional recommendations can be made for MBIp.