Innovation is a complex phenomenon and process involving translation of knowledge into new techniques, products, services. It is considered crucial for sustainable agriculture development and achievement of long-term food security. The review describes the diversity of innovation and relates it to agro-food sector. It also sheds light on different innovation models and explores their contribution to framing agro-food sustainability transitions. There are many variations in the use of the term ‘innovation’. Typical distinctions encountered in the literature are incremental vs. radical innovation and product vs. process vs. organizational innovation. A significant feature of the development of modern innovation thinking has been a gradual broadening of innovation scope as well as more attention to sustainability. The scope of innovation was broadened to include soft (social/organisation) innovations besides hard/technical ones. In fact, the interest has shifted from technological innovation to disruptive niche innovations fundamental for socio-technical transitions. Moreover, as recognition of system complexity, frameworks such as the Innovation systems and the Multi-Level Perspective (MLP) were developed and promoted. However, despite positive innovation benefits, relationship between innovation and sustainability in the agro-food arena is far from straightforward. Therefore, focus is gradually moving from innovation process to its impacts in terms of sustainability and its contribution to sustainability transitions in agriculture and food systems.