Psychologists in schools can play an important role in developing policies and programs to promote healthy eating habits. This study analyses the contributions of family socioeconomic status, peer influence (schoolmates' food consumption), and school-based nutrition interventions to explain adolescent eating behaviors. Data were obtained from the 2014 Health behaviour in school-aged children survey in Spain, with a sample of 6,851 adolescents (11- to 16-years-old). The results suggest that school-based healthy-eating programs could improve by considering parental education level and by implementing interventions focused on the peer social network. Policies that limit access to unhealthy products in schools--rather than simply offering healthy foods alongside unhealthy products--could be more effective.