Despite strong theoretical reasons to believe that the quality of parent–infant interactions should influence child sleep, the empirical evidence for links between maternal behavior and children's sleep is equivocal. Notably, it is unclear at which ages such influences might be particularly salient. The current study aimed to examine prospective longitudinal associations between early maternal sensitivity and children's sleep during early childhood. Maternal sensitivity was assessed at 12 months during a home visit. Children's sleep was measured at 12 and 18 months as well as at 2, 3, and 4 years, using a sleep diary completed by mothers. Results revealed significant or marginal positive associations between maternal sensitivity and children's sleep consolidation (percentage of nighttime sleep) at 2, 3, and 4 years, but not at the most proximal assessments of 12 and 18 months. These findings suggest that child age could potentially be a key factor in the associations between maternal behavior and children's sleep. Highlights Associations between three dimensions of early maternal sensitivity and children's sleep from 1 to 4 years of age were investigated. Maternal sensitivity was positively associated with children's sleep between 2 and 4 years, but not at 12 and 18 months. The results suggest that child age could be a key factor in the associations between maternal behavior and children's sleep.