Background: Coronavirus disease (COVID-19) was identified in China in December 2019. During any major epidemic, psychosocial disturbance occurs, which can surpass people's capacity to handle the condition. Objective: The study aimed to estimate the prevalence of anxiety disorder and to assess sleep quality among Egyptian adults during COVID-19 lockdown. Methods: The study was cross-sectional study through an anonymous web-based survey. Results: Majority of participants were females (80.3%), highly educated (96.8%), and with mean age of 32.9 ± 8.7 years. Nearly two-thirds were healthcare workers (65.5%). The overall prevalence of anxiety (generalized anxiety disorder score more than 9) was 42.5%. Nearly three-fourth (73.5%) of participants reported poor sleep quality (Pittsburgh Sleep Quality Index score more than 5). In the multivariate logistic regression models, being female (adjusted odds ratio = 1.75, 95% confidence interval: 1.13–2.7 for anxiety and adjusted odds ratio = 2.217, 95% confidence interval: 1.461–3.364 for poor sleep quality), younger than 35 years (adjusted odds ratio = 0.537, 95% confidence interval: 0.376–0.767 for anxiety and adjusted odds ratio = 0.578, 95% confidence interval: 0.397–0.841 for poor sleep quality), and focusing more time on COVID-19 news (adjusted odds ratio = 1.937, 95% confidence interval: 1.601–2.343 for anxiety and adjusted odds ratio = 1.494, 95% confidence interval: 1.219–1.83 for poor sleep quality) were significant predictors of anxiety and poor sleep quality. Conclusion: There was an increase in both anxiety and sleep disorders during COVID-19 pandemic. Young women spending more time on COVID-19 were at higher risk of developing anxiety and poor sleep quality. [ABSTRACT FROM AUTHOR]