Ecological infrastructure refers to naturally functioning ecosystems that deliver valuable services to people, such as filtered water and disaster risk reduction. With natural resources becoming scarcer, there is a growing interest in reinvesting in naturally functioning ecosystems in the form of ecological infrastructure, with the assumption that ecological infrastructure complements engineered infrastructure. In many low- and middle-income countries, ecological infrastructure interventions are seen as a key strategy to simultaneously alleviate poverty and improve ecosystem functioning. However, the socio-economic outcomes of ecological infrastructure investments remain poorly documented. We address this knowledge gap by synthesizing research (n = 53 cases) that analyses how ecological infrastructure investments affect ten different socio-economic dimensions, such as income and food security in low- and middle-income countries. We find that ecological infrastructure investments primarily lead to positive outcomes for short-term income and natural capital, whereas positive outcomes for other socio-economic dimensions are less frequently observed. Cases with a high degree of participant involvement in the early implementation of ecological infrastructure investments are significantly more likely to capture positive outcomes across a variety of socio-economic dimensions. Analogously, cases spanning multiple methods – rather than adopting either a qualitative or a quantitative approach – report positive outcomes across more dimensions.