This study seeks to integrate two research traditions that lie at the base of the understanding of personality pathology in adolescents. The first research tradition refers to normal personality according to the Five Factor Model (FFM). The second tradition specifies the key feature of personality disorder as the capacity to mentalize, which can be reflected in Social Information Processing (SIP). In a clinical sample of 96 adolescents, the authors investigated response generation, coping strategy, and memories of past frustrating experiences as part of SIP, as mediator in the relationship between personality and personality pathology, and a possible moderating role of personality on the relationship between SIP and personality pathology. The hypothesized mediation, by which the effects of personality dimensions on personality pathology was expected to be mediated by SIP variables, was found only for the effect of Neuroticism, most specifically on BPD, which appeared to be mediated by memories the patients had about past frustrating conflict situations with peers. Some moderating effects of personality on the relationship between SIP variables and personality pathology were found, suggesting that high Agreeableness and sometimes low Neuroticism can buffer this relationship. These results suggest that personality dimensions and social cognitions both independently and together play a role in adolescents' personality pathology.