Aging out of the care system strongly predicts later homelessness, yet little is known about how levels of contact with children’s social care influence youth homelessness, or whether risk peaks at particular ages.

We conducted a population-wide, retrospective cohort study of individuals born January 1995–December 1997, alive and resident in Northern Ireland during follow-up (July 2011–October 2022; aged 16–28 years). Homelessness data from the Northern Ireland Housing Executive were linked to social services, administrative, and health records. Cox proportional hazards models estimated age-specific hazard ratios (HRs) for homelessness risk from age 16, comparing young people with prior social care contact (“child in need” or “child in care”) to those without, adjusting for sex, area deprivation, settlement band, and mental ill health.

The cohort included 90,260 individuals contributing 869,524 person-years. More than half (54.6%) of those presenting as homeless had a history of children’s social care contact. Care experienced individuals faced the highest risk at age 18 (HRadj = 29.11, 95% CI 25.33–33.45), while risk among those with a child in need history peaked at age 17 (HRadj = 8.10, 95% CI 7.13–9.21), relative to peers with no social care history.

Young people with a history of social care contact are markedly overrepresented among the homeless population. The transition to adulthood (ages 17–18-years) is a critical period of vulnerability, underscoring the need for targeted interventions and enhanced support so social care experienced young people can enter adulthood without homelessness.