Development co-operation has traditionally been the playing field of governments, multilateral institutions, and established development NGOs. In the past decade, however, other actors in Northern countries (such as businesses, migrants' organisations, professional groups, and schools) have shown active interest in development-related activities. Although they do not belong to the epistemic community of development specialists and are often overlooked in the discourse and literature on development co-operation, their number and importance are growing. These novel approaches to development co-operation give rise to some important reflections about their methodologies, potential impact, and fundraising. Based on the authors' experiences and research in Belgium, the article raises some issues about what they term the fourth pillar of development co-operation, with the aim of stimulating the academic and policy-oriented debate.