Internationalisation of agricultural co-operatives is a worldwide trend and has been identified by several studies as one of the key challenges co-operatives are currently facing. This paper provides a comprehensive literature review of the internationalisation of agricultural co-operatives globally, including the identification of the critical factors in their development. Starting with a review of the traditional definition of co-operatives and their unique characteristics, the paper explores the emergence of new co-operative models, reasons for internationalisation as well as the barriers to it, forms of internationalisation adopted by co-operatives, and potential conflicts that can arise. The paper goes on with a new descriptive model for determining internationalisation of co-operatives. Finally, using the mentioned model, the paper includes case studies of two New Zealand co-operatives: Fonterra, a pure co-operative in the dairy industry and Zespri, a co-operative hybrid in the kiwifruit industry, and their internationalisation situation.