OBJECTIVES: To quantify racial/ethnic inequities in the use of harmful supplements sold with claims to aid in immune boosting, energy boosting, cleansing/detoxing, and weight loss throughout the first year of the COVID-19 pandemic. STUDY DESIGN: Prospective cohort study using longitudinal data (April/May 2020-April 2021) drawn from the US-based COVID-19 Substudy (N = 55,098), embedded in the Nurses' Health Studies 2 and 3 and the Growing Up Today Study. METHODS: Modified Poisson models were fit to estimate sociodemographic-adjusted risk ratios (aRRs) and 95 % confidence intervals (CIs) of supplement use by racialized identity. We estimated the contribution of social stressors in driving racial/ethnic inequities in use of immune, energy, cleanse/detox, and weight-loss supplements. RESULTS: Non-Hispanic Black participants had up to two times higher risk of supplement use compared to Non-Hispanic White participants. Living in a county with a high COVID-19 mortality rate was associated with a slightly elevated risk of immune supplement use, and experiencing chronic high discrimination was associated with an elevated use of all supplement types. CONCLUSIONS: There were stark racial/ethnic inequities in use of harmful supplements throughout the first year of the COVID-19 pandemic.