Whether COVID-19-related experienced stress influenced lifestyle habits remains to be thoroughly evaluated among university students. This study examined the relationship between COVID-19-related experienced stress and subsequent lifestyle habits among undergraduate students. This cross-sectional study included 708 undergraduate students from Université Laval (Québec, Canada) participating in the ExPan (Expériences pandémiques) cohort. Data on COVID-19-related experienced stress and lifestyle were self-reported using a questionnaire completed between February and April of 2022. A Stress Index (SI) was computed by summing scores associated with 31 situational statements related to the pandemic (e.g., not being able to see friends, dealing with job loss). A Healthy Lifestyle Score (HLS) ranging from 0 to 7 was calculated based on 7 lifestyle habits: moderate-to-vigorous physical activity, sleep quality, fruit and vegetable intake, tobacco and electronic cigarette use, alcohol consumption, cannabis use, and hard or sedative-hypnotic drugs use. In multivariable-adjusted models, a negative association between the SI and the HLS was found (10% increment SI=-0.23, 95% CI=-0.30, -0.16 HLS point; P<0.0001). The SI was also negatively associated with sleep quality, fruit and vegetable consumption, while being positively associated with at-risk alcohol consumption, cannabis use and hard or sedative-hypnotic drug use. Subgroup analyses suggested a negative relationship between the SI and HLS among participants who did not receive academic accommodations (e.g., additional time for evaluations, personal notetaker), but not those who received such accommodations. This study suggests that COVID-19-related experienced stress was negatively associated with healthy lifestyle habits in this cohort of undergraduate students.