Background <p>The delivery of income support interventions at an early age has positive short-term health impacts on children. However, less is known about whether those effects are sustained later in life. We addressed this question by systematically reviewing the literature on long-term (i.e., assessed after 5 + years) health impacts of income support interventions delivered in preschool age (in utero to 5 years).</p> Methods <p>We focused only on experimental or quasi-experimental studies, without country restrictions. We retrieved studies from subject-specific databases for general, mental health, and economics, and from citation searching. All the retrieved literature was double-screened at the title, abstract, and full-text stages. We performed a data extraction of the relevant information from the eligible studies and synthesised them via a narrative synthesis approach.</p> Results <p>Nine studies, eight quasi-experimental and one randomised control trial, were deemed eligible, all conducted in high or middle-income countries. These studies assessed several health outcomes, including overall mortality, cause-specific hospitalisation, mental health, and anthropometrics. Consistent long-term health improvements were observed from early income support interventions exposure across all the health dimensions assessed.</p> Conclusions <p>Despite knowledge gaps, especially in low-income countries, our results suggest that implementing income support interventions during preschool age can have a prolonged positive effect across several health dimensions. Implementing such policies and strategies would prove beneficial for health, alongside their main goal of reducing childhood poverty and health inequalities.</p>