Human papillomavirus (HPV) is the most common sexually transmitted virus in the world. Although HPV vaccine is an adolescent vaccine, a 'catch-up' vaccine is also recommended for 13 to 26 years-old females who have not been vaccinated previously and 13 to 21 years-old males who have not been vaccinated previously. The majority of Americans, however, reach adulthood without receiving the recommended HPV vaccine doses. Increasing the HPV vaccination series uptake requires theory-driven empirical understanding of factors influencing HPV-related decisions among this population. Based on the Social Cognitive Theory, the current study assessed the interaction between personal and environmental determinants of vaccine uptake and its effect on the behavioral intention to obtain the HPV vaccine. The San Diego State University Psychology Department participant pool was utilized to collect the data from 209 participants between the ages of 18 to 26 years who have not yet obtained any dose of HPV vaccine. Data were collected anonymously and analyzed using a series of seven correlation analyses, two hierarchical linear regression analyses, and three mediation analyses. The findings demonstrated that: (1) female gender and social influence (parents' and peer endorsement of HPV vaccine) significantly predicted behavioral intentions to obtain the HPV vaccine, p < .001; (2) controlling for gender, HPV vaccine-related attitudes and HPV vaccine-related self-efficacy significantly predicted behavioral intentions to obtain the HPV vaccine, p < .001; and (3) controlling for gender, both attitudes towards HPV vaccine and knowledge regarding the HPV vaccine significantly mediated the relationship between physician's recommendation and intention to obtain the HPV vaccine (both ps < .001). However, injection anxiety, knowledge about HPV vaccine, and physician's recommendation to obtain HPV vaccine were not significant predictors of participants' intentions to obtain the HPV vaccine. In an exploratory analysis, self-efficacy mediated the relationship between social influence and intentions to obtain HPV vaccine, p <.001. The present study offers understanding of personal and environmental factors associated with HPV vaccine decisions among college students, and also highlights the need for studying these mechanisms longitudinally in order to develop effective interventions to increase HPV vaccine uptake.