In this preregistered study, we tested the dark-ego-vehicle principle. This principle states that individuals with dark personalities, such as high narcissistic traits, are inclined to become involved in certain kinds of ideologies and political activism. We argue that narcissistic individuals can be attracted to anti-sexual assault activism because this form of activism may provide them with opportunities to obtain positive self-presentation (e.g., virtue signaling), gain status, dominate others, and engage in social conflicts to get their thrills. A diverse US sample (N = 313) completed online measures of narcissistic traits and involvement in anti-sexual assault activism. In addition, relevant covariates were assessed (i.e., age, gender, adult sexual assault history, sexual harassment myth acceptance, and altruism), and the interaction between narcissistic traits and gender was considered. The results of the multiple regression analysis showed that higher narcissistic traits predicted an individual’s higher involvement in anti-sexual assault activism over and above the covariates. However, this relationship was evident only for the women in this sample. Notably, a higher level of altruism in an individual was also substantially associated with higher involvement in anti-sexual assault activism. We discuss how the narcissism-by-gender interaction may be in line with the dark-ego-vehicle principle.