Background: Young adult cancer survivors are at risk for subsequent human papillomavirus (HPV)-related malignancies. High-risk sexual behavior increases risk for HPV acquisition; HPV vaccination protects against infection. We aimed to determine the prevalence of sexual behaviors, factors related to high-risk sexual behaviors, and the relationship between sexual behaviors and HPV vaccine non-initiation among survivors. Methods: Survivors at comprehensive cancer centers, aged 18–26 years and 1–5 years post-treatment, reported sexual behaviors and HPV vaccine initiation (i.e., ≥ 1 dose). Multivariable logistic regression was performed to calculate odds ratios (OR) and 95% confidence intervals (95%CI) for factors associated with high-risk sexual behaviors (age at first intercourse < 16 years, ≥ 3 lifetime sexual partners, or condom use ≤ 50% of the time) and to explore the relationship between sexual behaviors and vaccine non-initiation. Results: Of the 312 participants (48.1% female, median age at cancer diagnosis 17.2 years and at survey 20.9 years), sexual intercourse was reported by 63.1%. Of those reporting intercourse, 74.6% reported high-risk sexual behavior. Factors related to high-risk sexual behavior included currently dating/partnered (OR = 4.39, 95%CI 2.5–7.7, P < 0.001) and perceived susceptibility to HPV (OR = 1.76, 95%CI 1.3-2.5, P < 0.001). Most survivors (75.3%) reported HPV vaccine non-initiation; sexual behaviors were not associated with vaccine non-initiation (P = 0.4). Conclusions: Many survivors participate in high-risk sexual behaviors, yet HPV vaccine initiation rates are low. Factors related to high-risk sexual behaviors can inform interventions to reduce risk for HPV acquisition among survivors. Implications for Cancer Survivors: Cancer survivors participate in sexual behaviors that increase risk for HPV acquisition and would benefit from vaccination.