Objectives. To identify key effects of the pandemic and its economic consequences on menstrual product insecurity with implications for public health practice and policy. Methods. Study participants (n = 1496) were a subset of individuals enrolled in a national (US) prospective cohort study. Three survey waves were included (March‒October 2020). Menstrual product insecurity outcomes were explored with bivariate associations and logistic regression models to examine the associations between outcomes and income loss. Results. Income loss was associated with most aspects of menstrual product insecurity (adjusted odds ratios from 1.34 to 3.64). The odds of not being able to afford products for those who experienced income loss was 3.64 times (95% confidence interval [CI] = 2.14, 6.19) that of those who had no income loss and 3.95 times (95% CI = 1.78, 8.79) the odds for lower-income participants compared with higher-income participants. Conclusions. Pandemic-related income loss was a strong predictor of menstrual product insecurity, particularly for populations with lower income and educational attainment. Public Health Implications. Provision of free or subsidized menstrual products is needed by vulnerable populations and those most impacted by pandemic-related income loss.(Am J Public Health. 2022;112(4):675-684. (https://doi.org/10.2105/AJPH.2021.306674).