The current study used a dyadic framework to assess whether the rate with which men and women reciprocated their partners’ negative and positive affect with similar affect during conflictual topic discussions accounted for the association between each partner’s trait hostility and propensity to commit physical violence toward a romantic partner. Using Dynamic Development Systems theory and a community sample of at-risk men (N = 156) and their female partners, the hypotheses that poor relationship processes (indexed by quicker negative and slower positive affect reactivity) would account for physical IPV perpetration beyond trait hostility was tested. Results suggest that for women (but not men) quicker negative affect reactivity is a mechanism that partially explains the hostility-IPV association; whereas for men, trait hostility of both partners best explained their perpetration of physical violence. No support, however, was found for positive affect reactivity as a protective relationship process factor for IPV involvement. Findings are in line with other studies indicating men were less likely to engage in such negative reciprocity relative to women, which is consistent with prior findings that men show greater withdrawal or avoidance during conflict than do women (Christensen & Heavey, 1990). Furthermore, findings highlight the importance of clinicians emphasizing how both partner’s individual characteristics, as well as their communication patterns and emotion regulation processes germane to the romantic relationship, impact the likelihood of experiencing physical IPV.