Background: While sexually diverse adolescents and young adults present a 2 to 4 times higher risk of suicidal thoughts and behaviors than those who identify as exclusively heterosexual, very few longitudinal studies have been conducted to explore when suicidal thoughts and behaviors emerge in this population, and how they evolve from adolescence to adulthood. Furthermore, protective factors, such as perceived parental support, that could potentially mitigate this increased risk are poorly documented. Aims: This study aims to 1) describe the trajectories of suicide risk of sexually diverse youth from adolescence to young adulthood compared to their heterosexual counterparts in a Canadian cohort, and 2) explore the moderating role of perceived parental support and biological sex. Method: Data were drawn from the Quebec Longitudinal Study of Child Development (QLSCD) birth cohort. A 4-point suicide risk score was derived at age 13, 15, 17 and 23 based on self-reported past-year suicide ideation or attempts. Sexual orientation was assessed at age 23 based on participants' self-identification using The Klein Sexual Orientation Grid. Perceived parental support was self-reported at 12 years. Growth curve modeling was used to model suicide risk evolution from age 13 to 23. Interaction terms were added to the model to explore the moderating role of perceived parental support and sex at birth. Results: Among 1,323 youths from the QLSCD cohort, 25.9% identified as mostly heterosexual, bisexual, homosexual, or unsure/questioning. Sexually diverse youth showed an overall greater suicide risk from age 13 compared to those exclusively heterosexual, with a larger increase in suicide risk up to age 17, followed by a larger decrease. Suicide risk decreased as perceived parental support increased for both sexually diverse participants and those exclusively heterosexual. Irrespective of sexual orientation, females had a higher risk of suicide at age 13 than males. Females showed an increasing risk up to age 17 followed by a decline, whereas males presented a gradual increase in suicidal risk from age 13 to 23. Conclusions: Our study reinforces that the risk of suicide is higher among sexually diverse youth, and thus suggests that early implementation of tailored suicide prevention strategies is essential as their increased risk emerge early in adolescence, as young as age 13. Our results also support that strengthening parental support could be an important target for intervention to help reduce the risk of suicide from early adolescence onwards in all youth, regardless of their sexual orientation.