Lesbian, Gay, Bisexual, Transgender, Queer, and other sexual and gender minority (LGBTQ+) youth and young adults (YYAs) have poorer mental health outcomes than their cisgender, heterosexual peers in large part due to multilevel stigmatization and minority stress. This was exacerbated by psychological stressors stemming from the COVID-19 pandemic; these experiences intersected with YYA unique developmental stage. Here we explored LGBTQ+ YYA's pandemic-related experiences, focusing on intersections between stigma and belonging, developmental processes, and their relationship to mental health. We conducted qualitative interviews from August to November 2021 with 34 LGBTQ+ YYA ages 14 to 24; interviews were nested within a quantitative study on YYA experiences during COVID-19. Interviews were transcribed and coded using thematic analysis. YYA described how pandemic impacts like quarantine and isolation directly impacted their mental health; these coalesced around four types of thematic shifts: shifts in (1) time; (2) living situations; (3) community supports; and (4) social and political climate. Multilevel stigmatization also created new mechanisms of norm enforcement for LGBTQ+ YYA. Interviews demonstrated how the pandemic also impacted key developmental processes including identity formation and autonomy seeking. The potential consequences of these pandemic-related shifts largely depended on YYA's experiences of stigma and/or belonging throughout the pandemic. Findings suggested that isolation from the COVID-19 pandemic intersected with existing socio-ecological structures in LGBTQ+ young people's lives. Efforts to investigate longitudinal impacts of the pandemic, as well as to intervene to reduce the stigmatization experienced by LGBTQ+ YYA, remain urgent.