Hormonal and neuropsychological impairment in intimate partner violence (IPV) perpetrators could play a role in domestic violence. For characterizing whether there is a specific psychobiological response to stress, participants who had previously been jailed for IPV and controls were compared for testosterone and cortisol levels, tested for 2D:4D ratio (as an indicator of masculinization), and given several trait questionnaires and neuropsychological tests related to executive functions and theory of mind. After performing the Trier Social Stress Test (TSST), IPV perpetrators experienced decreases in salivary testosterone (T) levels, a moderate worsening of mood, slight anxiety, and a salivary cortisol (C) level increase. Moreover, high basal T was related with high levels of anger and anxiety and worse mood. However, that basal mood does not significantly alter T levels in response to stress. Nonetheless, controls experienced smaller changes in T and larger changes in C and psychological mood. With respect to neuropsychological and cognitive empathic features, IPV perpetrators showed poorer executive performance and emotional recognition than controls. In addition, deficits in both neuropsychological domains were positively associated. Regarding emotional empathy, IPV perpetrators showed higher levels of personal distress than controls. The 2D:4D ratio was lower in IPV perpetrators than in controls. Moreover, only in the former a smaller 2D:4D ratio was related to large increases in T in response to stress and poor emotional recognition. Together with social aspects involved in IPV, differences in psychobiological variables and their relationships could play a relevant role in the onset and perpetuation of violent behavior. Aggr. Behav. 39:355–369, 2013. © 2013 Wiley Periodicals, Inc.