BACKGROUND: The COVID-19 pandemic has resulted in adverse effects on individuals’ physical and mental health worldwide, with university students also being adversely affected by this process. OBJECTIVES: This research aimed to determine the mental condition, sleep quality, and eating behaviors of university students during the COVID-19 process. METHOD: This cross-sectional study was conducted with 1,065 university students. Study data were collected with an online questionnaire including a personal information form, the Depression Anxiety Stress Scale, the Pittsburgh Sleep Quality Index, and the Dutch Eating Behavior Scale. RESULTS: Students’ poor sleep quality was determined to be 69.5%. It was also determined that students’ depression and stress levels were moderate that their anxiety levels were low, their eating behaviors were generally problematic, and more than half had poor sleep quality. In addition, eating disorders and poor sleep quality increased as depression, anxiety, and stress levels increased, and eating disorders increased as poor sleep quality increased ( p < .05). CONCLUSIONS: The results emphasize the importance of the strengthening of students’ mental health, particularly by improving their sleep quality and eating habits. Evidence-based interventions regarding the effects of the pandemic should be made for students under the leadership of a psychiatric nurse, and effective strategies must be developed accordingly.