The role of attachment in shaping psychosocial processes has been studied extensively in the offline context, but little is known about parallel online processes. This study examined whether associations between attachment anxiety and responses to potentially negative partner behaviours (presented using vignette methodology) would be moderated as a function of whether hypothetical scenarios occur in online (face-to-face) or offline (social media) contexts. A total of 267 participants completed a measure of adult attachment (RAAS), and a relationship events questionnaire (R-REQ), in which participants rated their psychosocial responses to potentially distressing partner behaviours featured in online and offline scenarios (median age: 21 years; 81% female). Positive associations between attachment anxiety and cognitive, emotional, behavioural responses were seen across contexts; however, associations with emotional and behavioural (but not cognitive) responses were moderated by context, such that they were amplified in distress-matched online scenarios. These results suggest that social media represents a distinct context, with implications for computer-mediated communication and wellbeing links.