Purpose: The purpose of this study was to assess the prevalence of anxiety and depression symptoms and understand factors influencing mental health among dental health care workers (DHCWs) in the United States (US) during the COVID-19 pandemic.Methods: Beginning in June 2020, dentists (DDS) and dental hygienists (DH) in the US were invited to participate monthly in an anonymous, longitudinal, web-based survey. The Patient Health Questionaire-4 (PHQ-4) was used to estimate rates of anxiety and depression symptoms. Changes in mental health over time and differences by demographic and practice characteristics, COVID-19 community transmission level and COVID-19 vaccination status were tested using χ2 tests and multilevel multivariable logistic regression.Results: A total of 8,902 DHCWs (DH, DDS) participated in the survey for a response rate of 6.7%. Anxiety symptom rates peaked in November 2020 (28% DH; 17% DDS) and declined to 12% for both professions in May 2021. Depression symptoms were highest in December 2020 (17% DH; 10% DDS) and declined to 8% in May 2021. Controlling for gender, age, race, ethnicity and community COVID-19 transmission levels, DDS respondents had lower odds of anxiety symptoms (aOR 0.82; 95% CI 0.70 to 0.95) and depression symptoms (aOR 0.79; 95% CI 0.67 to 0.93) than DHs. Compared to vaccinated respondents, DHCWs who were unvaccinated but were planning on getting vaccinated had significantly higher rates of anxiety (aOR 1.71; 95% CI 1.20 to 2.44) and depression symptoms (aOR 1.57; CI 1.07 to 2.29).Conclusions: The mental health status of DHCWs fluctuated during the COVID-19 pandemic. Anxiety and depression were associated with the demographic and professional characteristics of the DHCW as well as the perceived risk of COVID-19 infection. Mental health support should be made available for all DHCWs.