Background: Medical students are at risk of poor mental health and burnout compared to general population age- and education-matched peers, which has future implications for patient care. Research has suggested that demographic factors can predict mental illness and burnout among medical students. However, less is known about predictors of mental health and how they compare to predictors of burnout, and few studies have examined multiple demographics simultaneously. Objectives: This study examined and compared demographic predictors (gender, ethnicity, age, level of education, year of study and proposed specialty) of mental health and burnout in first to fourth year Canadian medical students. Method: Medical students (n = 129) completed online surveys comprised of validated questionnaires. Results: Multiple regression indicated that third year [Beta] = -0.243, p = 0.013) negatively predicted mental health (R[superscript 2] = 15.0%). Female gender ([Beta] = 0.242, p = 0.005), 'other' ethnicities ([Beta] = 0.189, p = 0.028), third year ([Beta] = 0.391, p < 0.001) and fourth year ([Beta] = 0.212, p = 0.023) positively predicted burnout (R[superscript 2] = 32.7%). Female gender and fourth year predicted mental health and burnout differently. 'Other' ethnicity, second year and third year predicted mental health and burnout similarly. Conclusion: Findings fill gaps in the literature and may inform medical stakeholders in developing targeted programmes for improving medical students' mental health and burnout. Medical students with greater well-being can progress into physicians who will be more likely to promote well-being in their patients.