Many jurisdictions have legalised and licensed online gambling sites. Nonetheless, a notable proportion of the online gambling market operates offshore. Offshore sites pose risks for consumers in terms of unsafe and disreputable practices, compete with domestically-licensed sites, and do not participate in the economies in which they operate. This study aimed to explore the extent to which Australian online gamblers use offshore as compared to domestic gambling sites, consumer attitudes, and gambling-related harms. Participants (N=3,199) completed an online survey assessing gambling behaviour, reasons for choosing sites, awareness of and impact of online gambling legislation, and problem gambling. Results show that 25.8% of online gamblers used offshore sites, and that these were more involved gamblers overall than domestic gamblers, and had greater problem gambling severity. Most online gamblers preferred domestic sites, indicating that regulation of online gambling with associated consumer protection measures may benefit those who wish to gamble online.