This article discusses patterns in mental health of young Australians from age 19 through 25 and explores changes in mental health over these years. Data are derived from five waves of the Australian Life Patterns longitudinal study. The outcome variable in focus was self-reported mental health. Analyses were conducted in two steps using linear mixed models with both fixed and random effects. The analysis shows a negative linear trend in mental health status. The mental health of women was worse than that of men though a negative trend was found in both men and women. Though high socio-economic status (SES) individuals reported best mental health compared to their mid and low-SES peers, a negative trend was identified for them as well as for mid-SES participants. There is weak support for a negative trend among those of low-SES backgrounds. The study adds to evidence that there is a negative trend in mental health in young Australians but that this trend is not uniform across all young people. In light of this we argue the need for further research that analyses patterns of poor mental health in relation to social systems and institutions.