Integrative Behavioral Couple Therapy (IBCT) posits that emotional reactions to a partner's behavior can be as important to the relationship as the behavior itself. This study examined whether acceptance (a) is distinct from relationship sentiment, (b) mediates the link between a partner's behavioral frequency and own relationship satisfaction, and (c) mediates the association between frequency of partner behavior and frequency of one's own behavior. Both members of 307 married couples (N = 614 persons) completed self- and spouse-report measures of frequency and acceptability of positive and negative behaviors. Acceptance was distinct from satisfaction and mediated both relations for all types of relationship behaviors. Findings support IBCT's model of emotional-cognitive acceptance of partner behaviors as a key source of relationship distress.