Objective: We aimed to assess trends in anxiety and interruptions in disease-modifying antirheumatic drug (DMARD) use among patients with rheumatic diseases during the COVID-19 pandemic and to evaluate whether DMARD interruptions were associated with disease flares. Methods: ArthritisPower, the Vasculitis Patient-Powered Research Network, and other patient organizations invited members to join a 52-week longitudinal study, with baseline surveys completed March 29 to June 30, 2020, with follow-up through May 2021. Logistic regression incorporating generalized estimating equations evaluated associations between interruptions in DMARD use and self-reported disease flares at the next survey, adjusting for demographic characteristics, medications, disease, and calendar time. Results: Among 2,424 patients completing a median of 5 follow-up surveys, the mean age was 57 years, 87% were female, and the most common conditions were rheumatoid arthritis, vasculitis, and psoriatic arthritis. Average Patient-Reported Outcomes Measurement Information System (PROMIS) anxiety T scores decreased from April 2020 (58.7) to May 2021 (53.7) (P < 0.001 for trend). Interruptions in DMARD use decreased from April (11.2%) to December 2020 (7.5%) (P < 0.001) but increased through May 2021 (14.0%) (P < 0.001). Interruptions in DMARD use were associated with a significant increase in severe flares (rated ≥6 of 10) at the next survey (12.9% versus 8.0% [odds ratio (OR) 1.71 (95% confidence interval [95% CI 1.23, 2.36]) although not any flare (OR 1.18 [95% CI 0.89, 1.58])]. Conclusion: Anxiety and interruptions in DMARD use initially decreased over time, but DMARD interruptions increased during 2021, possibly related to an increase in COVID-19 cases or vaccine availability. Interruptions in DMARD use were associated with increased rates of severe disease flares, highlighting the importance of avoiding unnecessary DMARD interruptions.