While there is growing evidence for the effectiveness of mental health interventions in low- and middle-income countries and humanitarian contexts, this is lacking for psychosocial programming. We aimed to summarise the evidence for psychosocial programming in these contexts through a systematic review (PROSPERO: CRD42017069066) of peer-reviewed and grey literature of programme evaluations. A total of n = 42,435 unique records were initially identified, with n = 211 records meeting full inclusion criteria. We identified 51 randomised controlled trials of 47 different interventions. The remaining studies used different evaluation methodology. Only three interventions had more than one experimental/quasi-experimental evaluation: Brief Intervention and Contact, Problem Management Plus and Child Friendly Spaces. While there are many studies of interventions, it was challenging to identify the same intervention across studies, leaving almost no interventions with more than one rigorous study supporting their use and many interventions that are poorly described. This makes it difficult to choose between them or even to implement them. Future research should focus on replication of well-described interventions in multiple different sites, to place future intervention selection on a more scientific basis. There is also a need to better understand the impact of psychosocial programmes in sectors other than health and protection, such as nutrition. These sectors may provide critical delivery mechanisms for psychosocial programming to broaden the reach of such interventions.