The aim of this study is to evaluate the sleep behaviors of healthcare professionals working in secondary and tertiary hospitals in a large population in Turkey and to show how sleep quality is affected during the pandemic process by using the easily applicable Jenkins sleep scale (JSS). Methods The population of this cross-sectional descriptive study consists of two pandemic hospitals (2nd level state hospital and 3rd level university hospital) determined in Kahramanmaraş province. Data were collected between 03.08.2020 and 30.09.2020 with responses to online survey questions. The security of the data was assigned to SurveyMonkey enterprise. In our questionnaire, we asked subjective sleep quality (poor, moderate, high), sleep time (<24:00 and ≥24:00), time to fall asleep (minutes), total sleep time (hours), and medication use (sleeping pills). We also used Jenkins Sleep Scale Turkish version (JSS-TR) to assess sleep quality and the Epworth sleepiness scale (ESS) for increased daytime sleepiness. Results Healthcare workers who participated in our survey reported that they started to go to bed later, fell asleep later (mean: 41.75±35.35 minutes), their total sleep time (mean: 6.67±1.88 hours) was shortened, and they needed medication to sleep more (%5.7) after the COVID-19 pandemic. During the COVID-19 pandemic, bedtime behavior after 24:00 decreased from 80.1% to 43.9% of those who previously went to bed before 24:00. For those who went to bed after 24:00 before, it increased from 19.9% to 56.1%.In addition, sleep quality as assessed by subjective and JSS significantly deteriorated after the COVID-19 pandemic. Excessive daytime sleepiness increased. Those with ESS>10 before COVID-19 were 3.9%, post- COVID-19 ESS>10 14.1% (p<0.001). Conclusion The COVID-19 pandemic has significantly adversely affected the sleep behavior and sleep quality of healthcare professionals. The JSS is an easily applicable scale for assessing sleep quality in large population studies.