Background and aimsThe links between bullying victimisation and low self-esteem are well established. However, the relationship between physical activity (PA), bullying victimisation and self-esteem is still rather unexplored. The present study aims to investigate the moderating effect of PA on the relationship between bullying victimisation and self-esteem among young men. MethodsThe sample used for this study is based on registers of the Finnish Defence Forces and consists of questionnaire-based data collected from young healthy men (n = 146 767, aged 18–29 years, mean age 19 years) who started their conscript service during 2015–2021. Self-esteem was measured with the Rosenberg Self-esteem Scale and bullying victimisation and leisure-time PA (LTPA) with single questions. Unadjusted and adjusted linear regression models and the aligned rank transform Anova model were calculated. ResultsThe findings showed that there is a dose-response association of self-esteem with bullying victimisation and LTPA. Furthermore, a significant moderating effect of LTPA was found in the relationship between bullying victimisation and self-esteem. Vigorous LTPA at least once a week seems to lessen the negative effects of bullying victimisation on self-esteem. ConclusionsLTPA may have the potential to buffer against negative mental health outcomes resulting from past experiences of bullying victimisation on a young person's self-esteem. More opportunities for LTPA to support self-esteem among young people should be provided, especially for vulnerable groups and those with limited resources and possibilities to engage with PA.