The COVID-19 pandemic exacerbated existing mental health disparities between majority and minoritized identity groups, across factors including race, ethnicity, sex at birth, sexual orientation, and gender identity. Though each of these identities has been related to disparities in mental health, little empirical research assesses 1) the cumulative and synergistic impact of holding multiple marginalized identities upon mental health, as predicted by intersectionality theory, 2) how these identities interact with discrimination, or 3) how holding minoritized identities might shape psychological responses to significant events. Here we use data from a longitudinal survey of a national sample of adults (N=1070) during the COVID-19 pandemic to investigate how intersectionality relates to experiences of discrimination, stress, anxiety, and depression. For each participant, a Composite Intersectionality (CI) score was calculated as the cumulative count of minoritized identities across race, ethnicity, sex, sexual orientation, and gender identity. Greater self-reported discrimination as measured by the Everyday Discrimination Scale was associated with increased mental health symptoms. Higher CI was associated with greater anxiety, depression, and stress but relationships for those highest in CI were most evident when accounting for discrimination. Further, CI differentially impacted mental health trajectories following events such as the murder of George Floyd and the 2020 presidential election, particularly when accounting for discrimination. These results suggest that minoritized stress operates through multiple pathways. The impact of identity on mental health can be more aptly captured with an intersectional model that includes discrimination.