Objective: Since the coronavirus is very infectious, preventive measures are at the forefront in the fight against coronavirus disease-2019 (COVID-19). High disease prevalence, rapid increase in the number of patients and high additional workload increase the risk of transmission for health care workers (HCWs). This study aimed to evaluate the knowledge level of intensive care unit (ICUs) and operating room (ORs) employees about COVID-19.,Materials and Methods: This study analysed questionnaires of 480 HCWs in the ICU and/or OR. The participants completed a survey consisting of 29 questions that measured the level of knowledge of HCW on COVID-19 through manual methods or online.,Results: Our survey involved a total of 480 HCWs who comprised nurses (38.2%), doctors (27.7%), anaesthesia technicians (18.1%) and cleaning personnel (15.8%). For the question "What are high-risk factors of COVID-19?" the respondents answered age 61-80 years (90.6%), comorbidities (89.2%) and being a HCW (85.6%). On-the-job training on COVID-19 was given to only 46.9% of all participants. Moreover, 61.6% of the participants stated that they had hospital procedures on COVID-19. Social media (81.9%) was the most common source of information. In addition, 74.8% of the participants were anxious about COVID-19, and 63.4% said that they wear a surgical mask only when they contact patients.,Conclusion: To ensure continuity in health care, HCWs, especially cleaning personnel who are often in contact with patients suspected with or patients with confirmed COVID-19, should use personal protective equipment, undergo on-the-job training programmes on the pandemic at regular intervals and be screened routinely.