Many studies have examined how to reduce meat consumption and promote sustainable consumption, but very few studies have addressed this issue within the framework of the social contexts of eating. We conducted two experiments to examine how the context of commensal eating might influence people's food choices. In Experiment 1, we asked participants to imagine eating alone or with others, and then to choose three dishes from a choice set consisting of two meat and two vegetable dishes, so they had to choose between a meat-heavy meal and a vegetable-forward meal. Consequently, the participants showed a stronger choice preference for the meat-heavy meals in commensal eating compared to solitary eating, and the symbolic meaning of foods mediated this effect. In Experiment 2, participants were divided into different groups and primed with beliefs regarding the symbolic meanings of certain foods before making food choices. Consequently, the participants chose fewer meat-heavy meals in commensal eating after they were primed with the belief that vegetables could symbolize status and wealth, compared to those without such priming. Collectively, these findings reveal the mechanisms underlying the effect of commensality on the choices of meat-heavy meals, which has implications for nudging people toward making sustainable food choices in social settings.