Adolescents’ environmentally relevant behaviour is primarily carried out in a family context. Yet, it is usually studied and discussed in an individual decision-making perspective only. In a survey involving 601 Danish families, we examine to which extent adolescents’ everyday pro-environmental behaviour is the outcome of their own pro-environmental attitudes or the product of social influence within the family, that is, a reflection of the dominating values and norms in the family group as manifested most clearly in their parents’ attitudes and behaviour. In addition, we examine the moderating effects of two family characteristics, parenting style and the “generation gap” (parent–child age difference), on the relative weight of adolescents’ personalattitudes vs. social influences within the family as predictors of adolescents’ pro-environmental behaviour. Results show that the adolescents’ pro-environmental behaviour is heavily influenced by the dominating norms within the family and in particular by how strongly they are manifested in their parents’ behaviour.Source. A draft is not available online.