In situations when people have been drinking, they often find it difficult to tell their friends to stop drinking, or not to drive home. Most people want to avoid being seen as a busybody, which may inhibit advice giving. In the current study, we investigated how positive and negative descriptive and injunctive norms (in alcohol consumption contexts) affect people’s motivation to engage in intervening (e.g. ask a friend to stop drinking) and non-intervening (e.g. let friends make their own drinking decisions) behaviours. An online experiment with a four weeks post-test was conducted. Results showed that positive social norms resulted in a higher motivation to engage in intervening behaviour and a lower motivation to engage in non-intervening behaviour, compared to negative social norms. Injunctive, but not descriptive, norms had an effect on intervening behaviour four weeks after the manipulations. In line with prior findings, we also found that injunctive norms, in comparison to descriptive norms, are less amenable to change but that their influence is more enduring. Implications for theory and practice are discussed.