Background: Bullying victimization is a risk factor for social anxiety and disrupted classroom concentration among young people. Self-esteem has been implicated as a protective factor, but extant literature is sparse. Aims: Aim of present study was to test if a new measure of authentic self-esteem can buffer the negative effects of bullying victimization on social anxiety and disrupted classroom concentration concurrently and across time. Sample: A short-term longitudinal questionnaire design was employed with 836 12- and 13-year-olds. Methods: Peer nominations of bullying victimization and self-reports of authentic self-esteem were collected during winter term, and self-reports of social anxiety and disrupted classroom concentration were solicited then and also 5 months later. Results: Hierarchical multiple regression models indicated that authentic self-esteem moderated the association between bullying victimization and (i) social anxiety both concurrently and longitudinally and (ii) disrupted classroom concentration longitudinally. The Johnson-Neyman technique identified where on its scale authentic self-esteem had its buffering effects, and these were found to be at relatively low or moderate levels. Conclusions: Even moderate levels of authentic self-esteem can mitigate the association between being bullied and (i) social anxiety and (ii) disrupted classroom concentration. Efforts to monitor and where necessary enhance the authentic self-esteem of young people are warranted.