Effortful control (EC) has important implications for children's development. While both child sex and parenting are related to child EC, and while a literature shows early sex differences in children's responses to care, interactions between care and child sex in predicting EC are not well understood. We therefore examined associations between child sex and early caregiving as predictors of children's development of a specific aspect of EC, inhibitory control (IC). A community sample of 406 three-year-old children and their caregivers completed behavioural tasks and observational measures of parenting and IC, and children were re-assessed for IC at age 5. Results showed that early care influenced change in IC over time, although caregiving was a more important influence on boys' IC than girls; specifically, differences in boys' and girls' IC at age 5 were modest when parenting was positive. The implications of a better understanding of sex differences in associations between parenting and the development of IC in early childhood are discussed.