To account for generally low direct relationships between Big-Five personality traits and interpersonal citizenship behaviour (ICB), researchers have suggested that Big-Five traits are associated with such helping-related behaviour in interactive rather than direct fashion. This study investigated empathy as a potential moderator of Big-Five trait – ICB relations. Hypotheses were tested with data obtained from employees of a youth treatment facility and their supervisors. Results provided evidence that empathy interacts with three Big-Five personality traits, suggesting traits functioning at conceptually different hierarchical levels may jointly explain specific behaviours. Empathy could play an important role in understanding connections between these Big-Five traits and ICB.