This study examined the associations of passive and active online sexual risk behaviors with perceived family relationships, impulsivity, and attention-deficit/hyperactivity disorder (ADHD). A total of 176 adolescents with ADHD and 173 adolescents without ADHD participated in this study. The participants' parents rated their parenting style on the Parental Bonding Instrument. The adolescents self-reported their lifelong experiences of passive and active online sexual risk behaviors, perceived family relationship quality on the family domain of the Taiwanese Quality of Life Questionnaire for Adolescents, and three domains of impulsivity on the Barratt Impulsiveness Scale version 11. Multivariable logistic regression was used to examine the associations of online sexual risk behaviors with perceived family relationships, impulsivity, and ADHD. Overall, 114 participants (32.7%) reported passive forms of online sexual risk behaviors, and 49 (14.0%) reported active online sexual risk behaviors. Lack of foresight and self-control was significantly associated with passive online sexual risk behaviors (p = 0.003). Good family relationship was significantly associated with a decreased risk of active online sexual risk behaviors (p = 0.011), whereas seeking novelty and making decisions hastily was significantly associated with an increased risk of active online sexual risk behaviors (p = 0.048). ADHD diagnosis and inability to plan were not significantly associated with online sexual risk behaviors (p > 0.05). A high proportion of Taiwanese adolescents reported exhibiting online sexual risk behaviors. The factors related to the manifestation of these behaviors should be considered when designing relevant intervention programs.