Why are some diverse communities in sub-Saharan Africa able to achieve mutually beneficial collective action while others remain trapped in social dilemmas? This paper argues that inter-group trust plays an important role in explaining when and where communities succeed in collective endeavours. It develops an argument that illustrates how demographic contextual variables structure patterns of intergroup trust and prospects for local goods provision in diverse communities. It then assesses the argument by analysing community policing in two heterogeneous neighbourhoods in Cape Town, South Africa. The paper demonstrates how crosscutting cleavage structures in one Cape Town suburb bolstered the development of inter-group trust across the community, thus helping the community garner participation in community policing. It also documents how reinforcing cleavage structures in another Cape Town suburb has helped to suppress the development of inter-group trust, making the resolution of collective action problems more difficult.