Byline: Muna Abed Alah, Community Medicine Department, Hamad Medical Corporation (HMC), Doha, Qatar (Drs Abed Alah and Abdeen); Public Health and Preventive Medicine, Cairo University, Egypt (Dr Selim); Department of Family and Community Medicine (Dr Selim) and Community Medicine Department (Dr Bougmiza), Primary Health Care Corporation (PHCC), Doha, Qatar; Health Care Quality Management and Patient Safety Department (Ms Hamdani and Drs Radwan and Sharaf) and Strategic Planning and Performance Department (Ms Al-katheeri), Ministry of Public Health (MOPH), Doha, Qatar; and Community Medicine Department, College of Medicine, Sousse University, Tunisia (Dr Bougmiza).; Sami Abdeen; Nagah Selim; Dhouha Hamdani; Eman Radwan; Nahla Sharaf; Huda Al-katheeri; Iheb Bougmiza Abstract BACKGROUND: Being the first line of defense against COVID-19 infection, health care workers (HCWs) are at an increased risk of getting infected. Infection prevention and control (IPC) measures were deemed to be instrumental in protecting them and their patients against infection. PURPOSE: To assess HCWs' knowledge of IPC measures and their perceived effectiveness in protecting against COVID-19. METHODS: A national web-based survey was conducted in different health care sectors in Qatar. RESULTS: A total of 1757 HCWs completed the survey. HCWs believed in applying stricter IPC precautions while dealing with confirmed COVID-19 cases than with suspected cases. Males and physicians were more likely to have high perceived effectiveness of IPC measures than females, nurses, and pharmacists. Higher proportions of HCWs believed in the effectiveness of hand hygiene than most types of personal protective equipment. CONCLUSION: Further research is recommended to assess the impact of HCWs' knowledge and perceived effectiveness of IPC measures on their compliance.