Compulsory vaccination is a frequently implemented policy option for ensuring comprehensive vaccine coverage. Ongoing controversies around human papillomavirus vaccine dissemination, and suboptimal coverage, suggest the value of assessing acceptability of compulsory vaccinations-particularly among likely target populations-in advance of their public availability to support evidence-informed interventions. With the first HIV vaccine to demonstrate partial efficacy in a large-scale clinical trial, we examined individual characteristics and attitudes associated with support for compulsory HIV vaccination policy among a diverse, representative sample of adults attending probable HIV vaccine dissemination venues in a large urban county. Participants were recruited using three-stage probability sampling from likely venues for future HIV vaccine dissemination. We used Audio-CASI to administer a 60-min structured questionnaire. Items included endorsement of compulsory HIV vaccination policy, sociodemographic characteristics, injecting drug use, vaccine attitudes and perceived HIV risk. Among 1,225 participants (mean age = 36.8 years; 55.6 % males, 37.6 % non-English speaking Hispanic, 78.8 % heterosexual, 25.7 % injection drug users), almost half (48.2 %) endorsed a compulsory HIV vaccination policy. Non-English speaking Hispanics compared to whites, participants with less than high school education, higher positive vaccine attitude scores and higher perceived HIV risk were significantly more likely, and people who inject drugs significantly less likely to endorse compulsory HIV vaccination. Public health interventions to promote positive vaccine attitudes and accurate perceptions of HIV risk among vulnerable populations, and strategies tailored for people who inject drugs, may build support for compulsory HIV vaccination policy and promote broad HIV vaccine coverage.