Despite interruptions from work being increasingly common for many employees, their inherently disruptive nature induces strain on the work-life interface; yet, it remains unclear why the experienced strain is not universal. Drawing on role identity and Stress-as-Offense-to-Self theories, illegitimate interruptions from work (IIW) are inappropriate, avoidable, unnecessary, or unreasonable interruptions that carry an added meaning of disrespect, thereby presenting a threat to the self and potentially inducing additional unnecessary strain. Differential value placed on professional and personal roles likely shapes attributions of illegitimacy. We collected event-based data over five days from 182 employees (432 interruptions). Our multi-level moderated mediation model established IIW’s indirect effect on work-to-family conflict (WFC) via boundary violation, above and beyond the negative effects of interruptions themselves. Thus, subjectively ascribed illegitimacy induces further but potentially unnecessary negative strain. Men were more likely to experience boundary violation in reaction to IIWs, and subsequently reported more WFC as compared to women. Yet, although results suggest that IIWs may be a more salient immediate threat to men, it is possible that women’s higher threshold for IIWs may present a more distal threat for gender parity. We offer guidance for developing strategies to reduce IIWs and mitigate their impact.