African Americans in the United States (U.S.) are disproportionately affected by HIV. Developing an HIV vaccine is an important part of the HIV prevention and treatment toolkit and may help contribute to ending the HIV epidemic. To date, HIV vaccine trials have not engaged representative numbers of African Americans. We evaluated the willingness of African Americans to participate in HIV vaccine trials and identified correlates of willingness to participate (WTP) by surveying African Americans at low- and high-risk of HIV infection in a multi-site, cross-sectional study. We enrolled 1,452 participants; 59% heterosexual women; 21% heterosexual men; 20% men who have sex with men (MSM). Over half of participants (58%) expressed some level of WTP in HIV vaccine trials. Multivariable analyses revealed several variables were positively related to WTP: HIV risk behavior, knowing someone with HIV/AIDS, social support for trial participation, high perception of risk, perceived protection if in a trial, altruism, and greater tolerance for the ambiguous nature of trials (p<0.01). Emphasis on contextual factors related to personal HIV experiences, including knowledge of someone with HIV, and community support for research, may provide effective strategies for engaging African Americans in future HIV vaccine trials.