Using panel data from rural Peru, we explore the role of institutional thickness in furthering the effects of key infrastructure investments on pro-poor growth. Institutional thickness is characterised here as the result of a combination of four interrelated characteristics: a) the presence of organisations signalling collective action; b) the degree of productive asset inequality; c) the degree of inequality of opportunities; and d) the degree of political fragmentation. The paper shows that institutionally sound environments do contribute to amplifying the effects of public infrastructure on income growth for those belonging to the poorest tercile, allowing poverty to be more responsive to growth.