Abstract This study examines whether having delinquent friends interacts with other peer-related variables in the explanation of adolescent offending. We hypothesise that the relationship between delinquent friends and offending might be conditioned by the effect of (1) how much time they spend with their friends, (2) how much time they spend in unstructured routine activities and (3) their emotional relationship with their friends. To test these three hypotheses we use data from two independent samples of young adolescents in Halmstad, Sweden ( N = 1,003) and in Cologne and Freiburg, Germany ( N = 955). The results found strong support that the effect of delinquent friends on adolescent offending is conditional on the level of time they spend in unstructured routine activities. This indicates that delinquent friends have a stronger effect on offending for adolescents who often spend their free time in unstructured routine activities.