Whether or not child care provider characteristics and factors related to the care giving environment impact breastfeeding duration for working mothers has not been systematically studied. In this dissertation, I use Ecological Health Promotion Theory to explore the relationship between child care and breastfeeding through three different analyses. First, I interviewed nine child care providers to assess their knowledge, attitudes and beliefs about infant feeding and whether they vary on these factors across individuals and child care licensing types. Second, I conducted a small mail survey of 93 licensed child care providers in order to create a scale measuring attitudes on the importance of breastfeeding, breastfeeding program supports, and confidence in providing breast milk to infants in their care, and also to assess whether their attitudes and beliefs about breastfeeding are related to overall child care quality. Third, I use the National Institutes of Child Health and Development’s Study of Early Child Care to assess whether quality child care is associated with increased breastfeeding duration after controlling for work, demographic, and socioeconomic maternal characteristics. Through these three analyses, I found that child care providers to vary in their attitudes and programmatic supports of breastfeeding. Their personal experience breastfeeding their own infants was correlated with the proportion of infants breastfed in their program, and their attitudes, beliefs, program supports, and confidence in providing breast milk. Overall child care quality, as measured by traditional indicators (education/experience), were not associated with proportion of infants breastfed, personal experience, or breastfeeding attitudes and beliefs. In the third analysis, among working and non-working mothers, the proportion of time an infant spent in relative child care was associated with longer breastfeeding duration. Also, the younger the child when full-time child care first began, the sooner their mother weaned. However, when child care onset preceded work onset, breastfeeding duration increased. Finally, among working mothers, caregiver characteristics associated with quality had no significant association with breastfeeding after controlling for maternal characteristics. Proportion of time in a child care home was negatively associated with breastfeeding, but not for care giving in relative homes, or child care centers.