In 2020, COVID-19 began to affect adolescents' mental health, particularly cisgender girls and transgender/gender diverse (TGD) adolescents, who previously experienced a greater risk for depression and anxiety disorders than their peers. The present study investigated the moderating effect of gender on internalizing symptoms among three community samples of adolescents (N = 5,487; M[subscript age]= 14.7, SD = 1.4) throughout the first wave of COVID-19 (pre-pandemic, mid-first wave, and post-first wave). Rates of internalizing symptoms were highest for TGD adolescents at all timepoints, followed by cisgender girls, who were significantly higher than cisgender boys. Gender moderated the effect of time on internalizing symptoms. Specifically, internalizing symptoms increased only for cisgender girls. These results suggest that during widescale disasters, intervention should focus on those with previous vulnerabilities to mental health symptoms such as cisgender girls and TGD adolescents.