In all countries, informal systems of reciprocity influence the distribution of state resources. These social networks help people cope with adversity but can also promote favouritism and corruption, posing a dilemma for development practitioners. Using Papua New Guinea’s wantok system as a case in point, we develop a tripartite model for understanding how reciprocity networks function. This model provides insights into how practitioners can start designing context-specific responses to the challenges associated with informal systems of reciprocity.