Previous research found that social rejection leads to increased aggression. How can this aggressive behaviour be prevented? Four experiments demonstrate that reminders of social activity reduce aggression after social exclusion. A brief, friendly social connection with an experimenter (versus a neutral interaction) reduced aggression after social rejection. A traditional mood induction had no effect on aggressive behaviour, showing that an activity must be social to be effective. Participants who wrote about a family member, a friend or a favourite celebrity were also not aggressive after rejection. The effect was mediated by trust in other people but not by state self-esteem or mood. Rejected participants who have an alternative source of social connection eschew the increased aggression usually displayed after social exclusion.