Our study utilizes Australian survey evidence to estimate the heath and justice costs of a cohort of young homeless people. Health and justice costs for young homeless people are highly skewed with median costs well below mean costs. This is particularly true of justice costs resulting from a relatively high proportion of young homeless people having no interaction with the justice system. Having a diagnosed mental health condition is a primary driver of both health and justice costs. Having been homeless or sleeping rough in the previous year is associated with approximately four times mean health and justice costs compared with not having experienced homelessness. High justice costs are associated not only with having a diagnosed mental health condition homelessness and rough sleeping, but also a high-risk of dependence on one or more drugs or alcohol, identifying as Indigenous and a history of out-of-home care before the age of 18.