The relationship between unstructured socializing (peer‐oriented activity without supervision) and adolescent delinquency is widely established and recognized, but less is known about why this relationship exists. The present study integrates the unstructured socializing perspective with insights from social learning theory and other theoretical perspectives on peer influence and empirically investigates four possible explanatory processes. The study applies time diary data to operationalize accurately the concept of unstructured socializing and survey data to capture mediating variables and self‐reported delinquency (a general frequency measure of various offenses, as well as specified measures for violence, theft, and vandalism). Data were collected longitudinally with two waves of surveys and space–time budget interviews among 610 adolescents (11 to 20 years of age). A multilevel‐path model was estimated to analyze within‐individual changes over time. The findings indicate that three of the four proposed explanatory processes contribute to the explanation of the relationship between unstructured socializing and delinquency.