PurposeThis paper presents the most up-to-date comprehensive meta-analysis of the effectiveness of interventions to enhance psychological capital (PsyCap). It also reports the first meta-analytic examination of longer-term effects (beyond the immediate post-intervention period).Design/methodology/approachThis meta-analysis followed PRISMA 2020 guidelines and utilised the methodologies of Hunter and Schmidt (2004) and Borenstein et al. (2009). The search period was from 2006 until February 2023. A total of 40 studies (N = 4,207) were included in the meta-analyses. The analyses were performed using the Comprehensive Meta-Analysis (CMA) Version 4 software programme.FindingsThe results indicate that the impacts of interventions on PsyCap and each of its component resources are greater than those reported in a previous meta-analysis (Lupșa et al., 2020), with the strongest impacts on hope and optimism. Interventions had sustained positive effects on PsyCap, hope, resilience and optimism, but not efficacy, and the frequency of intervention sessions influenced the effectiveness of interventions on hope, efficacy and optimism. Interestingly, specific PsyCap-focussed interventions did not have the greatest impact on PsyCap or its component resources.Originality/valueThis study contributes to emerging research on wellbeing-oriented HRM and provides valuable insights into more effective design and implementation of interventions to enhance PsyCap and its component resources. These interventions are a promising form of investment in employees which may bring mutual gains for individuals and organisations. The present findings extend those of previous studies and specifically respond to the call for further research on the persistence of PsyCap intervention effects.