Public backlash against scientists is drawing growing concern. It can come from citizens, politicians, or journalists and ranges from legitimate criticism to harassment and physical attacks. Backlash also affects science communication professionals, yet this has received comparatively little public and scholarly attention. Our study addresses this gap. Drawing on qualitative interviews with 15 university communicators from multiple countries, we develop a conceptual model of their perceptions of public backlash, its effects on them and their institutions, their response strategies, and contextual factors. We introduce criteria for distinguishing legitimate criticism from illegitimate harassment and describe both negative and positive effects on science communication. The results show proactive and reactive response strategies and highlight the influence of topic characteristics, routes of backlash, and sociopolitical contexts. Overall, they offer a new perspective on the normative imperative for public engagement. We discuss implications for science communication research and practice.