Background Black and minority ethnic (BME) men who have sex with men (MSM) face a major burden in relation to HIV infection. Using a cross-sectional correlational survey design, the present study explored the relationships between HIV knowledge and reported sexual health and sexual behaviour in this population. Methods: A convenience sample of 538 BME MSM was recruited in London, Leicester and Leeds: 346 (64%) self-identified as South Asian, 88 (16%) self-identified as Latin American, 76 (14%) self-identified as Black, 13 (2%) self-identified as mixed, and 15 (3%) self-identified as other. Results: HIV knowledge was low across the board, and South Asian MSM manifested the lowest scores. Respondents who perceived their HIV risk to be low possessed the least HIV knowledge. There were interethnic differences in the frequency of gay sauna visits, sex-seeking on mobile applications, drug use and attendance at sex parties. Respondents reported a high frequency of racism and discrimination, with Black MSM reporting highest frequency. Conclusions: There is an urgent need to raise awareness of HIV in BME MSM, and a culturally competent approach to HIV awareness-raising in BME MSM is required. These findings shed light on the contexts in which HIV prevention efforts should be targeted to reach specific ethnic groups, as well as some of the potential syndemics that can increase HIV risk or undermine HIV outcomes in BME MSM patients.