ABSTRACT: Importance:Human papillomavirus (HPV) is the most common sexually transmitted infection in the United States, and oral HPV infection is associated with increased risk of oropharyngeal cancer. Objective:To describe the risk factors for oral HPV in sexually active female adolescents receiving the quadrivalent vaccine. Design, Setting, and Participants:Longitudinal cohort study involving repeated collection of oral rinse specimens from sexually active female adolescents conducted between October 19, 2007, and March 9, 2017, at a large adolescent health center in New York, New York, that provides free health care, including HPV vaccination. Exposures:Human papillomavirus vaccination and self-reported history of sexual behavior. Main Outcomes and Measures:Prevalence of HPV in the oral cavity. Results:Among the 1259 participants who were included in this study, median age at entry into the study was 18 (range, 13-21) years; 638 (50.7%) were of African American descent, 569 (45.2%) were of Hispanic descent, 43 (3.4%) reported another race/ethnicity, and race/ethnicity was unspecified for 9 (0.7%). The median (mode) age at first sexual activity was 14.8 (14) years, and 1161 (92.2%) reported having had oral sex. Human papillomavirus DNA was detected in baseline oral rinse samples of 78 of the 1259 participants (6.2%; 95% CI, 4.9%-7.6%). There was a significant decrease in oral HPV detection with time (in years) since first engaging in sexual activities, independent of age and concurrent detection of cervical HPV; comparing 4 or more years with 1 year or less, the odds ratio was 0.45 (95% CI, 0.21-0.96). Detection of vaccine types (HPV-6, HPV-11, HPV-16, and HPV-18) was significantly lower among participants who had received at least 1 dose of the quadrivalent HPV vaccine at the time of enrollment compared with those who were unvaccinated (odds ratio, 0.20; 95% CI, 0.04-0.998). Conclusions and Relevance:This study's findings suggest that detection of HPV in the oral cavity is not uncommon in sexually active female adolescents. In addition, HPV vaccination is associated with a significant decrease in detection of HPV vaccine types in the oral cavity.