PurposeOrganizational life and policy making is increasingly conceived in terms of a “three sector” model – public, private and “third”. The purpose of this research paper is to examine a little‐studied phenomenon that increasingly characterises societies in both the “developed” and the “developing” worlds. It aims to argue that these “sectors” have permeable boundaries, and that increasing numbers of activists and professionals operate across such boundaries, with important implications for policy and work.Design/methodology/approachThe research paper reports on a set of new ethnographic life‐work history data from the UK, Bangladesh and Philippines to explore experiences of people who cross between, or straddle, the third sector and the public sector.FindingsThe paper constructs a preliminary typology of boundary crosser archetypes for purposes of further analysis. This is based on motivations and levels of boundary crossing. Boundary crossing of this kind is linked with the concept of “work role transition”, and with the micro‐politics of policy contention.Practical implicationsThe paper concludes by suggesting that such work may offer new practical insights into strengthening the capacity of both third sector and government agencies.Originality/valueThe paper aims to be original in opening up this new topic for further discussion (and in particular problematizing the idea of sector boundaries), and through using the life history method to as part of organisational ethnography.