An important pathway by which relationships influence health may involve how people cope with interpersonal tensions. This study examined whether same day and previous day avoidance and engagement in arguments are differentially associated with self-reported well-being (emotional and physical) and diurnal cortisol patterns. Participants from Wave 2 of the National Study of Daily Experiences (N = 1,512; aged 33–84, 57% women) completed daily phone interviews for eight consecutive days and provided useable saliva samples that were assayed for cortisol for four of those days at specific times: waking, 30 min after waking, before lunch, and at bedtime. Multilevel models revealed same day arguments were associated with lower well-being (higher negative affect and lower positive affect) than same day avoidance or no tension. In contrast, previous day avoidance was associated with lower next day well-being (higher negative affect and more physical symptoms) and higher next day cortisol than having no interpersonal tension the previous day. Arguments have greater same day consequences for well-being, whereas avoided arguments have greater next day consequences, which may indicate delayed effects of avoidance.