This study presents the most robust evidence to date of the importance of engaging Indigenous children in early childhood education and care (ECEC) programs to boost cognitive and developmental outcomes in the short term (2 years after ECEC participation) and longer term (3–5 years after ECEC participation). We highlight differences between whether a child attended preschool or child care, and explore how the number of hours attended affects cognitive and developmental outcomes. Preschool attendance was associated with better short-term cognitive outcomes, as well as better cognitive and developmental outcomes in the longer term. There were not, however, significant effects associated with the number of preschool hours attended. Child-care attendance was associated with longer term cognitive and developmental improvements, but there is also some evidence that spending too long at child care can be detrimental to children’s developmental and cognitive outcomes.