In the past two decades, theoretical and empirical evidence suggests that communities of resource users are capable of overcoming social dilemmas, and are capable of creating and sustaining institutions designed to prevent degradation of common pool natural resources. However, there is incomplete understanding of what motivates this group-level behavior and why some communities are better adept at solving collective action problems than others. This paper specifically explores the role of group heterogeneity in collective action among forest communities in the northwestern Himalayas. Heterogeneity can have important social and ecological consequences and understanding both its nature and effects can help in neutralizing the negative and enhancing the positive. Based on data from 54 forest communities in Himachal Pradesh, India, this paper finds that heterogeneity has at least three dimensions: wealth, identity and interest, and each may significantly affect collective actions related to natural resource management. However, their effects are far from simple and linear.