Public health problems are often complex and ‘wicked’ in nature. Wicked problems have multi-factorial causation, are dynamic and often understood and acted upon differently by different actors. Multi-sectoral collaboration is increasingly emphasized for tackling wicked problems through developing a strategic multi-sectoral plan and then taking collective action. Critical systems thinking can support the development of a shared perspective of the problem, strengthen participation in collective action and foster reflective practices to continuously improve both problem understanding and action. In this paper, we present a critical collaboration model, drawing together two complementary theoretical frameworks, as well as insights from three case studies from New Zealand, to offer a systematic approach to adopting a critical systems perspective in public health collaboration. The model provides six questions to make explicit individuals’ understandings or assumptions about how others perceive an issue, problem or evidence, and the process of identifying answers strengthens the dialogical and reflective aspects of the collaboration. We indicate some potential areas for the application of the model to integrate critical systems thinking in collaborative practices.