AbstractInfants have the highest rate of admission into out‐of‐home care in Australia, with rising rates of entry to care occurring around the world. Our previous research identified children who entered care as infants as having high levels of developmental vulnerability. The objective of this study was to determine the child protection and developmental trajectories of children who entered care as infants and whether meeting developmental needs through service provision improves trajectories and outcomes for these children. This is a prospective cohort study using three waves (2011–2016) of survey data from the New South Wales Pathways of Care Longitudinal Study which includes standardised assessments (Age and Stages Questionnaire, Brief Infant Toddler Social Emotional Assessment and the Child Behaviour Checklist), as well as linked administrative child protection and health data. Our findings suggest that children who entered care as infants predominantly remained in the care system and had a high level of developmental vulnerability as infants. A large group had positive physical and cognitive developmental trajectories with service provision increasing over time; however, early service provision is needed. Another group was identified as having early social–emotional concerns and displaying worsening social–emotional trajectories. Intervention for this group is an important priority to reduce risk of ongoing poor mental health outcomes.