Childhood family adversity predicts adult interpersonal behavior and physiological responses to interpersonal stress. Additionally, negative marital behaviors (e.g., hostility and distress maintaining attributions) predict maladaptive stress responses and mental health problems, whereas positive marital behaviors (e.g., acceptance and relationship enhancing attributions) predict adaptive physiological and psychological outcomes. The present study examined potential marital behavior mediators and moderators of the link between childhood adversity and cortisol responses to conflict. In a sample of 218 different-sex newlywed couples, we examined (a) actors’ marital conflict behaviors as candidate mediators of the link between childhood adversity and cortisol responses to marital conflict discussions, and (b) partners’ marital conflict behaviors as candidate moderators of the relation between childhood adversity and cortisol responses to marital discussions. Path analysis using actor-partner interdependence modeling did not confirm mediation. Instead, wives’ childhood family adversity directly predicted husbands’ attenuated cortisol responses, and wives’ negative behavior predicted wives’ attenuated cortisol responses. As hypothesized, wives’ negative behaviors moderated the association between husbands’ childhood family adversity and husbands’ cortisol in response to conflict; husbands showed higher cortisol if they had experienced greater family adversity and if their wives displayed more negative behavior. Results suggest that childhood family adversity may carry forward to shape adult cortisol responses to conflict and highlights the importance of wives’ negative behavior for both husbands and wives. These findings add to the family psychology literature by further clarifying how the interaction of stressful childhood experiences and conflict behaviors in marriage are associated with adult physiological responses to conflict.