Victimization is a well-established driver of sexual minority youth's (SMY) mental health and substance use risk. The current study examined and extended this research by exploring how victimization, cybervictimization, and non-parental supportive adults contribute to SMY's vulnerability to poor mental health and substance use. Using data from the first representative sample of Texas youth that measures sexual identity, we analyzed sex-stratified models of the association between sexual identity, mental health, and substance use, and the confounding effects of victimization, cybervictimization, and non-parental adult support. Victimization was more common among SMY and accounted for a greater proportion of sexual identity disparities on mental health and substance use, especially for males. Sexual minority females were more likely to report cybervictimization than heterosexual youth, and cybervictimization was associated with mental health risk. SMY reported fewer available non-parental supportive adults, which was associated with more sadness, suicidality, and polysubstance use. Our study adds to extant evidence that victimization drives SMY's increased susceptibility to mental health and substance use risk. Schools should implement inclusive policies that prohibit bullying based on sexual minority identity and offer professional development opportunities for supporting SMY.