Achieving sustainable healthy diets for all will require substantial changes in individuals' food choices. Motivation plays a central role in behaviour change, yet little is known about the relationship between food choice motives and sustainability of the overall diet. The present study explored the relationship between food choice motives and different facets of diet sustainability in order to emphasize individuals' motivational supports and barriers regarding diet sustainability. We analysed food choice motives and dietary data collected through online questionnaires in 938 French adults (79% female, mean age ¼ 39y (SD ¼ 12)). The importance of nine food choice motives was assessed and three overarching motivational dimensions were derived from a principal component analysis on food choice motives: ‘health and sustainability, ‘ease and accessibility’ and ‘pleasure’. Food intakes were recorded using a food frequency questionnaire and six indicators of diet sustainability were calculated: nutritional quality, environmental impact, adherence to the EAT-Lancet diet, organic food consumption, local food consumption and ready-to-eat meals consumption. ‘Health and sustainability’ motives were consistently positively associated with diet sustainability indicators. On the contrary, ‘ease and accessibility’ motives were consistently negatively associated with diet sustainability. Associations between ‘pleasure’ motives and diet sustainability were mixed. Based on these results, it seems equally important to promote individuals' awareness of health and environmental impacts of food as to increase the accessibility of convenient sustainable healthy food products to support individuals' food choices towards sustainable diets.