Testosterone and cortisol have been proposed to jointly regulate aggressive behavior. However, few empirical studies actually investigated this joint relation in humans, and reported inconsistent findings. Also, samples in these studies were small and/or specific, and consisted largely of males. Therefore, in the current study testosterone and cortisol in relation to aggression were investigated in a non-clinical sample of 259 boys and girls (mean age 16.98 years, SD = 0.42, 56% boys). A positive testosterone/cortisol ratio, that is, high testosterone relative to cortisol, was found to be associated with aggressive behavior, explaining 7% of the variance. The interaction between testosterone and cortisol was not related to aggressive behavior and gender differences were not found. The ratio may reflect an imbalance leaving the individual more prone to rewarding aspects, than fearful of negative implications of aggressive behavior. Current findings indicate that this relation can be generalized to aggression in non-clinical adolescents.