Innovation as a policy goal, normative practice, and a conceptual framing of purposeful human activity, has received increasing attention. The question of what kinds of purposeful innovation might benefit smallholders in developing countries has been raised. This issue presents and analyses the work of Innovation Platforms (IPs) established by the COS-SIS (Convergence of Sciences–Strengthening Innovation Systems) programme in nine agro-enterprise domains in West Africa, drawing on Theory Guided Process Inquiry data recorded through 2011-end 2013. Six papers synthesise individual IP experiences, complemented by a cross-case analysis of external influences on the IPs and their responses, a reflection on how well the IPs in Mali dealt with local conflicts, and an analysis of how the work of the IPs in Ghana led to changes in university curricula and in the researching practices of three leading agricultural institutes. An analysis of thirteen case studies from Kenya, Benin, and South Africa supported by the JOLISAA (Joint learning in and about Innovation Systems in African Agriculture) programme, adds further insights. Five general lessons are drawn, expressed as propositions that can be further tested against others’ experiences: (i) IPs can bring about significant socio-technical and institutional changes at a range of levels, and in a wide variety of agro-enterprise domains and contexts; (ii) the IPs are not isolated from nor independent of the networks of influence in which they are embedded; thus they cannot be treated as the sole causal agents of the changes accomplished; (iii) research that tracks the IPs’ work and performance provides evidence that enables the members to learn from experience and adjust activities in the light of effects; (iv) there is no blueprint for what an IP is nor a recipe for the processes by which such changes are brought about; the form, activities, and changes co-evolve with whatever is happening in the wider context; (v) field-based diagnosis of opportunity, evidence-based information-sharing and experimental exploration of pathways of change establish the legitimacy and influence of IPs.