The adoption of sustainable diets is essential to maintain our planet’s ecosystem and the well-being of its inhabitants. Scientists characterize sustainable diets by four essential dimensions: respectful of the environment, of good nutritional quality, culturally acceptable, and economically fair. The ‘sustainable diet’ concept, however, can be challenging for consumers to understand. They might partially understand the concept or have representations of the concept that are not shared between individuals, which could result in difficulty putting the recommendations into practice. Our study investigated French consumers’ social representations of sustainable diets, aiming more particularly to show if groups with different levels of education might have different representations. A free word association task was carried out by 273 participants aged between 20 and 60 years. Our results revealed common associations among the participants, including concepts such as ecology, health, environment, and locality. Sociocultural and economic dimensions were rarely mentioned, unlike the predominant environmental dimension. Segmentation analysis by education level revealed that participants in the higher education group had more multidimensional social representations. These results show that the ‘sustainable diet’ concept is not fully shared by French consumers. Clarifying the definition should improve consumer understanding, thus promoting the adoption of sustainable diet practices by all.