The authors used data from the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development (N = 1,364) to examine maternal work hour status and parenting (sensitivity and learning opportunities) from infancy through middle childhood. Work hour status was conceptualized as nonemployment, part time, and full time. Adjusting for covariates, mothers employed part time had higher sensitivity scores and higher provision of child learning opportunity scores than did mothers who were not employed, and these differences characterized families during early childhood rather than middle childhood. Mothers' provision of child learning opportunities was greater when she was employed full time (vs. part time) during early childhood. In addition to child age, mothers' ethnic minority status and partner status moderated the association between maternal work hour status and mothers' parenting. In general, the findings supported ideas forwarded by role expansionist theory.