BackgroundMental health concerns are common among undergraduates and have been linked to lifestyle factors. This study examined the relationship between recreational screen time at university entry and mental health over the academic year, and the potential moderating role of self-esteem.MethodsData from the longitudinal Queen's U-Flourish Survey (2021/2022) included measures of screen time unrelated to academic work (leisure and social) and validated screening measures for anxiety (GAD-7), depression (PHQ-9), insomnia (SCI-8), disordered eating (SCOFF), and low well-being (SWEMWBS). Multivariable log-binomial regression was used to examine associations between screen time and mental health.ResultsAt entry to university, a higher proportion of males (n = 394) than females (n = 1,135) reported averaging 4 +  hours/day of leisure screen time (57.4% vs. 45.3%, P < 0.001), while a greater proportion of females reported 4 +  hours of social screen time (32.2% vs. 25.2%, P = 0.01). Higher screen time was associated with increased risk of clinically significant levels of symptoms and reduced well-being at school entry, with greater effects for leisure compared to social screen time. Students reporting 7-9 and 10 +  hours/day of leisure screen time were more likely to screen positive for anxiety (by 20% and 39%), depression (39%; 47%), insomnia (22%; 55%), and low well-being (45%; 68%) compared to students averaging ≤3 hours/day. Effects were comparable between males and females, except greater leisure screen time was associated with increased risk of disordered eating among females only. Associations between screen time and screening positive at the end of the academic year were largely attenuated. Leisure screen time ≥3 hours/day was most strongly associated with anxiety and depression among students with higher self-esteem.ConclusionsRecreational screen time ≥3 hours/day is common among first-year undergraduates and associated with higher levels of anxiety and depressive symptoms and lower well-being. It should be considered in campus mental health promotion and prevention efforts.