For college students, holding a minoritized, stigmatized sexual orientation, gender identity, or both (SOGI) may have compounded the stress and upheaval of the COVID-19 pandemic, impacting not only their ability to freely express their SOGI but also their mental health and well-being. Using minority stress theory and mixed methodologies, we examined associations among lesbian, gay, bisexual, transgender, queer, questioning, or other sexual and/or gender diverse (LGBTQ+) college students' (N = 368, Mage = 20.5) perceived pandemic-related changes in SOGI expression, internalized LGBTQ+ stigma, and mental health. Consistent with minority stress theory, students who thought the pandemic restricted their SOGI expression and who had more internalized LGBTQ+ stigma had worse mental health than their peers. In addition, students who thought the pandemic restricted their SOGI expression perceived that their mental health worsened due to the pandemic. The importance of SOGI expression for mental health during the pandemic has implications for tailored university programming to support LGBTQ+ students' mental health during times of stress and transition beyond the pandemic. Lesbian, gay, bisexual, transgender, queer, questioning, or other sexual and/or gender diverse (LGBTQ+) college students who thought that the pandemic restricted their sexual orientation or gender identity (SOGI) expression had worse mental health than their peers and were more likely to perceive that their mental health worsened due to the pandemic. Findings underscore the importance of SOGI expression and the need for programs to support SOGI expression, especially during times of stress and transition, to promote mental health among LGBTQ+ young people.