Intimate partner aggression (IPA) is a costly and incompletely understood phenomenon. Negative urgency, the tendency to act impulsively in response to negative affect, is predictive of IPA perpetration. Mindfulness, by virtue of its emphasis on nonreactivity to negative affect, is an opposing force to urgent tendencies that may mitigate the negative urgency-IPA link. Yet, no research to date investigates the interactive effects of negative urgency and mindfulness on IPA perpetration. Two studies were conducted that measured and manipulated multiple facets of mindfulness alongside measures of negative urgency and tendencies of IPA perpetration (combined N = 508 undergraduate students in monogamous intimate relationships). Counter to our preregistered predictions, we found that negative urgency’s association with greater IPA perpetration increased at higher levels of mindfulness. These findings suggest that mindfulness may not be a protective factor against IPA perpetration for individuals higher in negative urgency, but rather may serve as a risk factor.