Most children in the United States experience nonparental child care during early childhood, and many children experience changes in their care during this period. Changes in care, or child care instability, have been argued to disrupt children's emerging relationships with others and may impede children's social-emotional development, particularly when changes occur during infancy and toddlerhood. Data for this study were drawn from the Family Life Project, a longitudinal study representative of families living in rural low-wealth areas. With a sample of 1292 children who were followed from six months to prekindergarten, this study examined the associations between cumulative child provider instability (measured as overall changes or changes across or within settings) from 6 to 36 months and children's social adjustment at prekindergarten. A number of factors were included to control for family selection into child care. Results suggested that more overall child care provider instability was negatively associated with teacher ratings of social adjustment at prekindergarten. This association was driven by provider instability across but not within settings, though effect sizes were small. These findings point to an increased need to understand how early child care instability may be related to children's subsequent development.