Background and Objective: Health care workers were at risk for poor mental health during the COVID-19 pandemic. We investigated whether they experienced a change in the occurrence of depression and associated factors. Methods: Data comes from the COVID-19 HEalth caRe wOrkErS (HEROES) Study. The baseline wave 0 in Czechia was conducted in June 2020 (n=1,778) followed by wave 1 in spring 2021 (n=1,840). Depression was defined as =≥ 10 points on the Patient Health Questionnaire. Logistic regression estimated odds ratio (OR) with 95% confidence interval (CI) for the association of participants´ individual and work-related characteristics, simultaneously entered into the model, with depression. Results: In wave 0, 11% of the participants had depression, while 22% had depression in wave 1. Irrespective of wave, depression was associated with stress (OR 4.38; 95% CI 3.25-5.95), physical illness (OR 1.5; 95% CI 1.14-1.97), contact with COVID patients (OR 1.53; 95% CI 1.04-2.25), necessity to prioritize patients (OR 1.90; 95% CI 1.34-2.68), stigmatization (OR 1.64; 95% CI 1.25; 2.17), and experience of death due to COVID (OR 1.46; 95% CI 1.06-2.00). Lower odds of depression were predicted by resilience (OR 0.32; 95% CI 0.26-0.40), male gender (OR 0.62; 95% CI 0.44-0.86), sufficient personal protective equipment (OR 0.72; 95% CI 0.54-0.95), trust in management (OR 0.65; 95% CI 0.45-0.94), and professions of physician (OR 0.51; 95% CI 0.31-0.84) and nurse (OR 0.48; 95% CI 0.26-0.80) when compared to working in management. Age, education, informal daily caregiving, support from loved ones, work sector, and change in work tasks were not associated with depression. Conclusions: The occurrence of depression in health care workers in Czechia has doubled during the pandemic. Both individual and work-related factors seem to have played a role.