Objective To assess the awareness and acceptability of pre-exposure prophylaxis (PrEP) among men who have sex with men (MSM) and use sociosexual media at high risk of HIV infection in four Celtic nations.

Design Cross-sectional study.

Methods Online self-complete survey of 386 HIV-negative/status unknown MSM who reported condomless anal intercourse (CAI) with ≥2 men in the last year, recruited from gay sociosexual media.

Results One-third (34.5%, 132/386) of the participants were aware of PrEP but over half (58.5%, 226/356) reported that they would be willing to use PrEP if it were available to them. Only men who regularly tested for HIV every 6 months (adjusted OR 2.89, 95% CI 1.54 to 5.42) were more likely to be aware of PrEP. PrEP acceptability was only associated with reporting ≥5 CAI partners (OR 2.04, 95% CI 1.2 to 3.46) in the last year.

Conclusions Low levels of PrEP awareness were reported across these Celtic nations. Only one-third of high-risk MSM had heard of PrEP but over one-half would be willing to take a daily pill to prevent HIV infection. Sociodemographic factors, commercial gay scene proximity and social network use were unrelated to considering PrEP use. However, those reporting most CAI partners were more likely to consider PrEP use.