AbstractAdolescents' involvement in bullying situations is—at least partially—personality trait‐activated. Although some studies investigated personality correlates of bullying and being victimized, little is known about personality correlates of bystander responses (i.e., reinforcing, outsider behavior, indirect defending, and direct defending). The present study investigated whether Dutch adolescents' self‐reported HEXACO personality traits could explain their peer‐reported involvement in bullying (N = 552; Mage = 13.4 years, SD = 0.8 years). The results show that bullying was negatively related to honesty‐humility, emotionality, agreeableness (for boys specifically), and openness, whereas reinforcing was only negatively related to honesty‐humility and openness. Conversely, direct defending and outsider behavior were positively related to honesty‐humility, emotionality, and openness, whereas indirect defending was only positively related to emotionality and openness. Furthermore, reinforcing was positively related to extraversion (for boys only), whereas outsider behavior was negatively related extraversion and positively to conscientiousness. Finally, being victimized was positively related to emotionality and negatively to extraversion. These findings contribute to our understanding of the heterogeneity in adolescents' involvement in bullying and fit the view of bullying and defending as strategic and goal‐directed behavior. Implications for bullying prevention programs are discussed.