This cross-sectional study examined the mediating role of three reasoned action approach (RAA) constructs—attitudes, perceived social pressure, and perceived behavioral control—on the relationship between peer networks and intention to consume unhealthy food. The authors examined self-reported data of a sample of 277 adolescents from public and private schools in Lima, Peru. Results revealed a total mediating effect of the reasoned action constructs; yet attitudes and perceived behavioral control, but not perceived social pressure (injunctive and descriptive norms), mediated the relationship between peer network and intention to consume unhealthy food. Explanations for these results are discussed in light of social cognitive theory and Ajzen and Fishbein’s postulates about specific attitudes. Finally, we discuss how school nurses can take advantage of RAA variables to influence food environments, use peer networks for reducing unhealthy food consumption, and organize workshops to inform parents about the mechanisms that promote junk food intake.