This study explores the relationship between entrepreneurship and collective identity in an informal, or ‘slum’, community in Nairobi, Kenya. In Nairobi, as in cities across the Developing World, slum communities stand out as islands of poverty and neglect amidst increasingly cosmopolitan urban surroundings. Extant research, much of which centres on the so-called ‘Base of the Pyramid’ (BoP), has shown that where social groups experience levels of social and economic disadvantage which are far in excess of comparable groups, entrepreneurship is often underpinned by a strong collective orientation. This can have a profound and wide-ranging bearing on the venturing process. Slum communities, however, have yet to be considered in this research and, moreover, they remain largely neglected within the broader literature on entrepreneurship at the BoP. Drawing on ethnographic data collected during four-and-a-half months of fieldwork, I observed that collective identity was closely tied up with economic informality. Entrepreneurs believed that their community’s marginal status afforded them a de facto right to circumvent the costs of registration and taxation, considerably reducing the barriers to market entry in an environment characterised by widespread and acute resource deprivation. However, for most entrepreneurs this was the only facet of the venturing process that was permeated by collective identity. Navigating the many challenges of their market context was seen as an individual rather than a collective concern. This was observed to differ, however, among the slum’s younger generation, who, for the most part, had grown up there or moved there as adolescents. This cohort exhibited a stronger proclivity towards collaboration in entrepreneurial venturing, and their ventures were firmly rooted in dense, close-knit friendship networks. This study extends current understandings of how entrepreneurship is affected by social-group membership, particularly in a BoP context.