The Gudaga Study is a prospective, longitudinal birth cohort study of Australian urban Aboriginal children. Mothers of Aboriginal infants were recruited using a survey of all mothers admitted to the maternity ward of an outer urban hospital in Sydney. These data established initiation rates among Gudaga infants and those of non-Aboriginal infants born locally (64.7% and 75.2%, respectively) and factors associated with breastfeeding. Older (relative risk, 1.24; confidence interval, 1.01-1.44), more educated (relative risk, 1.30; confidence interval, 1.11-1.48) mothers who intended to breastfeed (relative risk, 2.22; confidence interval, 2.12-2.3) were more likely to breastfeed. Smokers (relative risk, 0.72) and mothers of Aboriginal infants (relative risk, 0.78) were less likely to initiate breastfeeding. Breastfeeding rates for Gudaga infants dropped rapidly, with 26.3% breastfeeding at 2 months. Local health services providers can benefit from such information as they target relevant prenatal, perinatal, and postnatal services for Aboriginal mothers and their infants.