Image-based abuse (IBA) refers to the non-consensual taking, sharing or threat to share nude or sexual images. Research suggests people who witness IBA behaviours can reduce the extent and impacts of its harm by taking action to intervene. However, there is limited research available on the attitudes, experiences and role of bystanders in the prevention of IBA. This paper presents findings from a national study examining bystanders’ experiences of, and responses to, witnessing IBA. Informed by a survey of 245 Australian adults in four jurisdictions, this paper shows that while witnessing IBA is common, few respondents reported taking action to intervene, and there are gender differences in bystander readiness to intervene. The findings have important implications for the development of bystander intervention and education programs.