The act of eating together, known as commensality, is an evolved mechanism of human life. Nonetheless, the association of commensality with food choice in adults is unclear, particularly in the United States where there is wide availability of highly processed food (e.g., ice cream, chips). The association may differ based on the social role of co-eaters, but this has not been fully examined. The present study was a cross-sectional survey of a nationally representative sample of the adult population in the United States (N = 750; Mage = 45.10 ± 16.45; 62.7% White; 50.4% women) conducted online in January 2020. Participants were recruited from double-opt-in market research panels and answered questions regarding commensality, food choice, and sociodemographic information. American adults chose more highly processed food when eating with friends compared to all other co-eaters. Adults with higher versus lower body mass index chose more highly processed food when eating alone. Adults with less versus greater income chose more highly processed food when eating with others, and younger versus older adults, Black versus White Americans, and women versus men chose more highly processed food when eating with others and alone. By considering intersections among commensality, food choice, and culture in adults, social scientists and consumers can identify social eating behaviors that may undermine or support health-promoting dietary change. Choosing minimally processed food like fruit and vegetables when eating with friends may be optimal for American public health.