This study examines the mental health trajectories of future/current undergraduate university students relative to their age-matched community peers from the ages of 15 to 21. It analysed data from the Household, Income and Labour Dynamics in Australia survey. The sample comprised 442 students and 1292 peers. Mental health was assessed with the five-item Mental Health Inventory from the Short Form 36. The results showed that students generally had better mental health than their peers. This was largely associated with better parental mental health and socio-economic position. However, the models also revealed reductions in the mental health of students relative to their peers at ages prior to major transitions in their student careers. This study contributes to the literature on university student mental health by comparing the mental health trajectories of students with their community peers and by identifying the ages when student mental health programmes may be of most benefit.