A comprehensive model for routine multi-disciplinary health assessment for children in out-of-home care was piloted in a Norwegian region. This paper reports on identified service needs and mental disorders among 196 children (0–17 years) receiving the assessment. Cross-sectional data was extracted from assessment reports. Results show needs across a range of services, with a mean of 2.8 recommended services for children aged 0–6 and 3.3 for children aged 7–17. Mental disorders were identified in 50% of younger children, and 70% of older children. For all children, overall service need was associated with mental disorders, in addition to male gender among younger children. Need for specialized mental health services was associated with mental disorders among younger children and increasing age among older children. The high frequency of service needs and mental disorders illustrate the importance of offering comprehensive health assessments routinely to this high-risk child population and necessitates coordinated service delivery.