Background: In the face of the COVID-19, as a public health emergency, the restaurant industry is struggling to organize itself. The aim of this study is to determine the knowledge, attitude, and practice and also the perceptions of restaurants' customers and managers toward COVID-19 prevention.Methods: This cross-sectional study was conducted using the mixed-method approach. Two online questionnaires were undertaken through WhatsApp Messenger among the 210 customers and 50 managers of restaurants. Multivariate linear regression analysis was conducted to identify the predictors of knowledge, attitude, and practice toward COVID-19 prevention. Then semi-structured, in-depth phone interviews were conducted with 45 subjects to identify their perceptions about the restaurant industry during the COVID-19 pandemic.Results: The majority of customers had moderate knowledge (72.4%), positive attitude (90.5%), and desirable practice (38.6%); whereas the majority of managers had sufficient knowledge (50%), negative attitude (82%), and acceptable practice (58%) toward the prevention of COVID-19 in restaurants. Multiple linear regression analysis showed with increasing each 10 years in the age of the customers, the practice score significantly decreased (Beta = −0.155, p < 0.05). Moreover, qualitative results revealed three categories (1. restaurant industry, 2. social media, and 3. government) in 9 themes with 32 sub-themes which were explored based on the perception of the participants toward COVID-19 prevention in restaurants.Conclusion: The majority of restaurant customers and managers have sufficient knowledge and acceptable practice, but a positive attitude among customers and a negative attitude among managers about the prevention of COVID-19 were shown. There is an urgent need to understand public awareness about preventing COVID-19 in restaurants at these critical moments. The results seek to provide strategies for the policymakers and restaurant industry to plan the specific educational intervention about how to manage future crises and public health improvement.