Mental health disparities have been reported among sexual minority individuals; minority stress theory posits that such disparities are a result of stigma and discrimination. We estimated the prevalence of mental disorders across sexual orientation groups among first-year college students and whether differences across sexual orientation groups varied by gender and country-level LGBTQ+ (lesbian, gay, bisexual, transgender, queer) social acceptance. Using data (N = 53,175; 13 countries) from the World Mental Health Surveys International College Surveys, we performed multilevel logistic regressions to estimate the associations between sexual orientation (i.e., heterosexual, heterosexual with same-gender attraction [SGA], gay/lesbian, bisexual, asexual, questioning, and other) and five twelve-month DSM-5 disorders (major depressive disorder, generalized anxiety disorder, panic disorder, alcohol use disorder, drug use disorder). Heterosexual students with SGA (AORs 1.30–2.15), gay/lesbian (AORs 1.49–2.70), bisexual (AORs 2.26–3.49), questioning (AORs 1.38–2.04), and “other” (AORs 1.76–2.94) students had higher odds of all disorders compared to heterosexual students with no SGA; asexual students did not. Significant interactions with gender show that the gender difference in prevalence was greater among bisexual individuals for most disorders and among all sexual minorities (except “other”) for drug use disorder. Significant interactions with country level LGBT+ social acceptance showed some sexual minority groups had lower odds (AORs 0.83–0.95) of disorder as country-level acceptance increased. These findings provide further evidence of mental disorder disparities across a wide range of sexual orientations and how these disparities vary by gender and societal LGBTQ+ acceptance in students from diverse countries.