Abstract Background Students enrolling in higher education often adopt lifestyles linked to worse mental health, potentially contributing to the peak age onset of mental health problems in early adulthood. However, extensive research is limited by focusing on single lifestyle behaviors, including single time points, within limited cultural contexts, and focusing on a limited set of mental health symptoms. Methods The UNIversity students’ LIFEstyle behaviors and Mental health cohort (UNILIFE-M) is a prospective worldwide cohort study aiming to investigate the associations between students’ lifestyle behaviors and mental health symptoms during their college years. The UNILIFE-M will gather self-reported data through an online survey on mental health symptoms (i.e., depression, anxiety, mania, sleep problems, substance abuse, inattention/hyperactivity, and obsessive/compulsive thoughts/behaviors) and lifestyle behaviors (i.e., diet, physical activity, substance use, stress management, social support, restorative sleep, environment, and sedentary behavior) over 3.5 years. Participants of 69 universities from 28 countries (300 per site) will be assessed at university admission in the 2023 and/or the 2024 academic year and followed up for 1, 2, and 3.5 years. Discussion The study portrays a unique opportunity to comprehensively understand how multiple lifestyle behavior trajectories relate to mental health symptoms in a large international cohort of university students.