This study examined the associations between individual differences in romantic attachment and transgression frequency and reactions in daily life. Data from both members of the heterosexual relationship were collected to examine how a persons’ attachment orientation influenced their own and their partner’s perceived transgressions and reactions to these transgressions. Across 10 days, 139 heterosexual couples reported on perceived transgressions by their partner. If transgressions occurred, they also reported on subsequent reactions such as forgiveness and rumination. Actor–partner interdependence models were used to investigate actor and partner effects of attachment anxiety and attachment avoidance on the number of experienced transgressions and reactions to transgressions. Attachment anxiety was not predictive with respect to any of the outcomes of interest. Higher attachment avoidance predicted fewer transgressions and more revenge in reaction to transgressions in men but not in women. Higher levels of attachment avoidance predicted more avoidance and rumination following a transgression. Additionally, a partner effect from attachment avoidance to avoidant reaction was observed. Findings are discussed regarding how attachment may account for differences in appraisal processes and emotion regulation strategies when confronted with relational transgressions.