Numerous studies show that intelligence and impulsiveness are important predictors of academic achievement in adolescence. However, it is not clear what contribution is made by the big five personality traits, because some studies suggest that Conscientiousness, Extraversion and Openness to experience are predictors while others show precisely the opposite. Direct aggression, through its relationship with impulsiveness, is another factor that has been linked to academic achievement. However, no previous studies have been made on the relationship that indirect aggression and psychological maturity have with academic achievement. For this reason, the purpose of this study is to determine the relative importance of psychological maturity, indirect aggression and the big five personality traits in predicting academic achievement in adolescents. As was expected, results show that intelligence and impulsivity are important predictors of academic performance. As far as psychological maturity is concerned, only the Work orientation component is related to academic performance. However, indirect aggression is not related to academic performance. The results pertaining to the big five personality traits suggest that Conscientiousness and Openness to experience are important for predicting academic achievement.