Psychoeducational interventions for family carers of people with psychosis are effective for improving compliance and preventing relapse. Whether carers benefit from these interventions has been little explored. This systematic review investigated the effectiveness of psychoeducation for improving carers' outcomes, and potential treatment moderators. We searched for randomised controlled trials (RCTs) published in English or Chinese in eight databases. Carers' outcomes included wellbeing, quality of life, global morbidities, burden, and expressed emotion. Thirty-two RCTs were included, examining 2858 carers. Intervention duration ranged from 4 to 52 weeks, and contact times ranged from 6 to 42 hours. At post intervention, findings were equivocal for carers' wellbeing (SMD 0.103, 95% CI − 0.186 to 0.392). Conversely, psychoeducation was superior in reducing carers' global morbidities (SMD − 0.230, 95% CI − 0.386 to − 0.075), perceived burden (SMD − 0.434, 95% CI − 0.567 to − 0.31), negative caregiving experiences (SMD − 0.210, 95% CI − 0.396 to − 0.025) and expressed emotion (SMD − 0.161, 95% CI − 0.367 to − 0.045). The lack of available data precluded meta-analysis of outcomes beyond short-term follow-up. Meta-regression revealed no significant associations between intervention modality, duration, or contact time and outcomes. Further research should focus on improving carers' outcomes in the longer-term and identifying factors to optimise intervention design.