This study examined the COVID-19-related knowledge and attitude towards COVID-19 and associated mental health status during COVID-19 among the students of Sultan Qaboos University in Oman using an online cross-sectional survey conducted from 26 March - 25 April 2021 among the students of Sultan Qaboos University (SQU). Both descriptive and inferential statistical techniques, including multiple logistic regression analysis, were used for data analysis. Of the 1,951 respondents, 60% were females with a mean age of 22 years. About 13% were tested COVID-19 positive and 3.6% were tested positive. Overall, students demonstrated a high level (81%) of knowledge and a positive attitude (83%) towards COVID-19. Knowledge appeared as a significant predictor of positive attitude. Despite the high level of knowledge and positive attitudes, there prevails some misconceptions or stigma to a group of students as about one-third of the students opined COVID-19 was a natural catastrophe and 13% of students were in favor of keeping it secrete if infected. The study documented a high prevalence of mild to severe levels of depression (66.3%), anxiety (69.2%), and stress (71%) among the students. Younger age, female, undergraduate students, single marital status, college of study, and good knowledge about COVID-19 appeared as significant predictors of mental health problems among the students. For improving the mental health and well-being of the students, the SQU authority should provide feasible psychological support to the students, with particular attention to the identified sub-group of students. Efforts should be made to remove the COVID-19-related stigma through mass-media campaigns.