Causal modeling was used to test the hypotheses of the theory of planned behavior for the prediction of prenatal breastfeeding intentions and postpartum breastfeeding outcomes with 135 childbearing women. In support of the theory, prenatal breastfeeding attitudes and perceived behavioral control predicted breastfeeding intentions (R2 = 23); however, the subjective norm variable failed to meet statistical criteria for model entry. Breastfeeding intentions weakly predicted duration of breastfeeding up to 6 weeks postpartum (R2 = .04). No additional empirically suggested prenatal and postpartum variables increased the explanatory power of the model in predicting breastfeeding intentions and duration. Implications for practice and research are discussed.