We study the intra-household spillover effects of South Africa’s Older Person’s Grant—a large unconditional cash transfer—on the mental health of women who are pregnant or who recently gave birth. We first document two stylized facts. First, while depression risk declines with increased wealth, women show higher levels of depression risk than men across all wealth deciles. Second, among women, depression risk spikes during pregnancy and only slowly declines in the months following childbirth. Next, leveraging the age-eligibility threshold of the Older Person’s Grant and restricting our sample to mothers who live with an older person near the eligibility threshold, we show that the grant, which increases household income, reduces risk of perinatal depression. The magnitude of the effect on depression risk is large enough to effectively eliminate the increased risk of depression associated with pregnancy and childbirth observed in our data. These results demonstrate the importance of improved economic environments, via existing social protection programs, in supporting the mental health of women before and after childbirth.