The world is suffused with self-organised groups asserting themselves in the policymaking corridors of governments and private-for-profits in order to jointly address stubborn societal challenges characterised as wicked problems. These self-organised bodies, labelled the third sector, operate in the advanced, developing, as well as less developed countries. This paper reviews the contemporary background of the third sector, its conceptual basis, its identity crisis and prospects for future development in the context of public governance in Nigeria. It does so premised on an orientation towards new governance tradition and heuristics. It argues that a better understanding of the concept, and governance role of the sector, by government policymakers, private-for-profits, and third sector actors themselves, will strengthen home grown cross-boundary collaboration for a more effective service delivery across the country.