In the context of sustainable agricultural development, the provision of other services beyond production is becoming a priority. We contend that a functional approach to agrobiodiversity is the best approach to meeting such goal in both research and agricultural practice. We have traced the development of studies on agriculture-biodiversity relationships referring to two milestones that had tremendous impact on research: the United Nation’s Convention on Biological Diversity (1992) and the Millennium Ecosystem Assessment (2005). Interest in the functional aspects of agrobiodiversity, i.e. the potential or actual provision of ecosystem services, has boomed in the latest 15 years, yet use of the term ‘functional biodiversity’ is still scarce. We propose a trait-based definition of functional biodiversity and a four-step methodology that should shed light on the potential of elements at each agrobiodiversity level – from gene to species and habitat – to provide single or multiple agroecosystem services in any context.