Numerous theoretical models of relationship distress suggest that strong, negative reactions to conflict are directly associated with lower levels of relationship satisfaction. Consistent with this supposition, substantial evidence links higher levels of subjective negative emotion, more pronounced and frequent expressions of negative affect, and higher levels of negative communication behaviors to lower levels of relationship satisfaction (e.g., Bradbury, Fincham, & Beach, 2000, Journal of Marriage and Family, 62(4), 964). However, the evidence linking stress-related physiological responding during relationship conflict and relationship satisfaction is less compelling than would be anticipated based on theory. We propose that these theoretically unexpected but empirically well-replicated findings may be the result of different patterns in association between physiological reactivity and relationship satisfaction for couples with varying styles in how they typically perceive unwanted behavior in one another. The present study tests negative attributions for undesirable partner behaviors as a moderator of the association between heart rate reactivity (HRR) during relationship conflict and relationship satisfaction in a sample of 60 married couples. A significant interaction emerged between HRR and negative attributions of partner behavior in predicting relationship satisfaction such that higher levels of HRR were associated with lower levels of relationship satisfaction for individuals who typically made more negative attributions for undesirable partner behaviors, but with higher levels of relationship satisfaction for individuals who typically made fewer negative attributions for undesirable partner behaviors. Implications for conceptualizing reactivity during relationship conflict and couple interventions are discussed.