The study investigated the associations among personality (Big Five model), attachment and psychosocial functioning in a nonclinical sample of 323 Greek preadolescents. Results indicated that positive personality traits were negatively associated with psychopathological symptoms, and positively with prosocial behavior. Perceived attachment moderated the relationship between openness and conduct problems, where the negative effect of openness on conduct problems was more pronounced for insecurely attached preadolescents. Finally, extraversion moderated the relationship between perceived attachment and conduct problems, thus acting as a protective factor to the conduct problems of insecure preadolescents. Results are discussed for their practical implications.