Lesbian, Gay, Bisexual, Transgender, Queer and Asexual (LGBTQA+) youth have a greater odds of experiencing stressful life events like discrimination and violence when compared to their cisgender heterosexual peers, which can lead to mental health problems. We aimed to estimate the prevalence of mental disorders among LGBTQA+ youths from the 3rd wave of the Brazilian High-Risk Cohort for Psychiatric Disorders (n= 1,475). Mental disorders were assessed using the Brazilian version of the Development and Well-Being Behavior Assessment. Sexual orientation, gender identity and biological sex were assessed using specific questions of a self-report confidential questionnaire. Data were analyzed using sampling weights to account for attrition and our oversampling design. The mean age was 18.14 years (SD=2.00) and 15.18% of the sample described themselves as LGBTQA+ (n=221). The LGBTQA+ group presented higher rates of anxiety disorders (30.14% vs. 13.37%; OR= 3.66; 95%CI: 2.82 - 4.75; p<0.001), depressive disorders (27.75% vs. 15.34%; OR= 2.51; 95%CI: 1.92 - 3.27, p<0.001) and post-traumatic stress disorder (4.98% vs. 2.25%, OR= 4.21, 95%CI: 2.54 - 6.96, p<0.001), if compared with the cisgender heterosexual group. No difference was found for conduct disorders (2.97% vs. 5.21% OR= 0.81; 95%CI: 0.39 - 1.69; p=0.577) or attention deficit hyperactivity disorder (5.92% vs. 3.28%, OR= 1.29; 95%CI: 0.74 - 2.25; p=0.361). Our results elucidate the mental health disparities between LGBTQA+ people and cisgender heterosexuals in Brazil. It highlights the need to promote the inclusion of this population in policy formulation and to support actions to mitigate and prevent the suffering and mental health problems related to sexual orientation and gender identity.