ObjectivesUnacceptable experiences (UEs) during undergraduate studies and the associated emotional and academic impact have not been rigorously evaluated in the Canadian context. This study aimed to estimate the prevalence of UEs and examine their associations with mental health and academic outcomes in a diverse sample of Canadian undergraduate students.MethodsUndergraduates attending Queen's University completed the U-Flourish Student Well-Being Survey at the beginning and end of each academic year from 2021/2022 to 2023/2024. Validated self-report measures included the GAD-7 (anxiety), PHQ-9 (depression), C-SSRS (suicidal thoughts and behaviours) and WEMWBS-7 (well-being). UEs reported over the academic year included: discrimination, sexual violence/harassment, bullying, hate crimes and physical assault. Multivariable regression analyses examined associations between UEs and student mental health outcomes and cumulative grade-point average (GPA) abstracted from the university database.ResultsNearly one-third (28.9%; range = 27.0-30.1% across years) of students (n = 2,948) reported experiencing at least one UE over the academic year. Discrimination (14.6%) and sexual violence/harassment (14.4%) was reported most frequently, followed by bullying/harassment (10.6%), hate crimes (5.0%) and physical assault (3.2%). UEs were highest in students who identified as non-binary gender (51.6%), 2SLGBTQIA + (39.9%) and as having a lifetime mental illness (41.2%). Each UE increased the risk of screening positive for anxiety and depression over the academic year by 10-19% and 14-40%, respectively. Students reporting UEs were also more likely (13-72%) to report having suicidal thoughts and/or behaviours over the academic year, particularly those reporting sexual violence (RR:1.72; 95% CI:1.45-2.05). Sexual violence, bullying, and hate crimes were associated with lower average cumulative GPA in first year.ConclusionUEs were commonly reported by undergraduate students, especially in minoritised subgroups, and associated with mental health concerns and academic difficulties. These findings highlight the need for further research to inform universal and targeted prevention and early intervention initiatives.