Men who engage in transactional sex with men (MTSM) are a high-risk population for HIV and other sexually transmitted infections. Epidemiological data have so far included them in the broad category of men who have sex with men (MSM), while research on transactional sex typically focused on female sex workers. The internet has substantially changed sex work practices and earlier findings concerning the sexual health needs of MTSM may no longer be applicable. We analyzed quantitative data from MSM based in the UK (n = 11629) taking part in the European MSM Internet Survey (EMIS-2017). Compared to non-MTSM, MTSM (n = 230; 2%) were younger, more likely to self-identify as an ethnic minority, be single, have lower education levels, struggle financially, and-controlling for age-more likely to be living with diagnosed HIV. Commonly unmet needs among all MSM were a lack of confidence in accessing HIV post-exposure prophylaxis, uncertainty about HIV status, and ignorance of where to access hepatitis vaccinations. Compared with other MSM, MTSM were notably less satisfied with the safety of their sexual practices, less confident in their ability to maintain sexual boundaries, and more likely to engage in risk because of absent precautionary resources. Given their greater opportunity for sexual risk, as well as fewer resources for negotiating safety, our findings suggest that services should prioritize MTSM in HIV prevention and sexual health promotion, including assertiveness and social skills training, in addition to knowledge-based education.