Situated within the context of concerns about sustainability and the over production and consumption of foods from animals the paper extends the emerging social science research field that addresses the ‘de-animalisation’ of the food system to explore societal debate around the substitution of foods from animals. Non-dairy milks (NDMs), made from legumes, nuts, seeds and grains provide a novel empirical case. NDMs are a substitute for dairy milk, a totemic food within national diets across the global North but one that to date has received limited attention within investigation of food system de-animalisation. A frame analysis is employed to explore how different food system actors make sense of the relationship between NDMs, dairy milk and food system sustainability. Identification of frames is undertaken through a qualitative methodology in which thematic analysis is conducted of exploratory primary data (seven semi-structured interviews) and secondary textual data from a wide range of sources. Two ‘pro NDM’ and one ‘pro dairy’ frames are identified, each associated with distinct groups of food system actors and emphasising different dimensions of sustainability. The paper concludes by reflecting on what the analysis reveals about substitution as a strategy within food system de-animalisation and the politics and governance of this process, and also offers suggestions for social science research into these issues.