There is a strong, bidirectional association between social disadvantage and poor mental health. The risk of experiencing mental health problems is particularly enhanced by factors associated with living in poverty. Thus, economic interventions may be effective in reducing the burden of mental health issues in these populations. This article explores the evidence based on one specific type of economic intervention on mental health, that is, supplementing household income through cash transfers. This narrative evidence is supplemented by an in-depth analysis of one of the world’s largest national cash transfer programs, the Bolsa Família program, in Brazil. We report that evidence from multiple contexts clearly demonstrates that cash transfers are highly effective in reducing the burden of mental health issues and reducing mental health disparities. We then consider the specific mechanisms through which cash transfers influence mental health. Finally, we discuss the need for these interventions and, referring to the Brazilian case study, explore potential strategies for their implementation at scale and the implications for research and policy.