From a public health perspective, raising awareness of gambling-related harms may activate a sense of personal threat that can encourage positive behaviour change and reduce experienced harm. This study sought to determine existing levels of gambling harm awareness, both in total and by specific harm types, across a nationally representative UK sample of 10,157 adult gamblers (4,951 female). It also explored the relationship between gambling harm awareness and problem gambling severity, after controlling for various demographic variables and gambling motives. Participants were recruited via an online panel survey and provided self-reports of past-year gambling participation, motives, problem gambling severity, and awareness of different types of harms. The harm awareness measure used a prompted vs. unprompted cueing methodology and framed harms as either betting- or gambling-related based on a previously reported semantic distinction. Results showed that prompting significantly increased the number of harms reported, while harm framing did not. Regardless of condition, participants reported greater awareness of resource harms (e.g., financial difficulties) compared to health and relationship harms, and a quarter of the sample did not report any type of betting/gambling harm. Based on the results of a hierarchical linear regression, gambling harm awareness explained significant variability in problem gambling severity scores. Increased gambling severity scores were associated with greater awareness of health harms and decreased gambling severity scores were related to greater awareness of resource and relationship harms. These findings raise concerns about the overall effectiveness of current public health efforts in increasing harm awareness and suggest the need to broaden their focus to support individuals of varying risk levels in recognising and addressing a wider range of gambling-related harms.