This paper explores the contribution the capability approach (CA) and grassroots innovation (GI) literature makes to a better understanding of the complexity, richness and specificity of bottom-up processes of social innovation (SI), and their specific contribution to social transformation. Using a purely qualitative methodology, the paper addresses a case study organic food buying groups in the city of Valencia and examines them through the lenses of SI, GI and CA. By taking four concurrent dimensions of the SI literature (agents, purposes, drivers and processes) and crossfertilising them with the bottom-up, people-driven character of GI, and the concepts of agency, capabilities, deliberative democracy and conversion factors from the CA, the paper creates a novel framework that we call Grassroots Social Innovation for Human Development. The analysis shows the potentiality of this novel framework to illustrate the elements that a bottom-up SI process should include in order to contribute to human development.