In two studies (N= 504) we looked through the lens of Reinforcement Sensitivity Theory to understand the Dark Triad traits (i.e., narcissism, psychopathy, and Machiavellianism). In Study 1, the Dark Triad traits were correlated with negative affectivity, reward sensitivity, the fight system, and dysfunctional impulsivity. In Study 2, the Dark Triad traits were associated with a fight response. Sex differences in the Dark Triad traits were present in Study 1 but proved more allusive in Study 2, but were mediated by individual differences in fight systems (Study 2) and reward and punishment sensitivity (Study 1). Narcissism was associated with Behavioral Activation and Inhibition Systems across studies and measures. Results are consistent with the adaptive coordination expected by evolutionary psychologists who study the Dark Triad traits.