The aims of this study were to develop a new measure of impulsive aggressiveness, and to assess whether this measure was associated with deficits in mentalized affectivity and adult attachment styles in a sample of 637 non-clinical participants. Extending Fonagy and Bateman's (2004) hypothesis, the mediating role of poor affectivity mentalization in the relationship between insecure attachment styles and impulsive aggression was also evaluated. Selected insecure attachment styles (R2(adjusted) = .18, p < .001) and deficits in mentalized affectivity (R(2)(adjusted) = .25, p < .001) were significantly associated with impulsive aggressiveness. The overall regression model accounted for roughly 33% of the variance in impulsive aggressiveness. Mentalization deficits significantly mediated the effects of attachment styles on impulsive aggressiveness, although effect size measures suggested that only partial mediation occurred.