The purpose of this study was to evaluate knowledge of breastfeeding issues among post-partum women who had participated in a prenatal program at the Rio de Janeiro Federal University (UFRJ) Maternity Teaching Hospital. The sample totaled 135 post-partum women who answered a structured questionnaire with objective questions about practical and theoretical aspects of breastfeeding. The women had begun prenatal care at the 16th week of gestation on average, with an average of 8 medical consultations. Some 53.3% stated having received information about breastfeeding during prenatal care, and 22.2% stated that the information they remembered the best was that they should breastfeed for the first 6 months. Regarding the best moment for the first feeding, 50.4% identified it as immediately after delivery. Some 47.4% said breastfeeding protects the child from diseases. Thus, although the mothers demonstrated basic knowledge about breastfeeding, issues like the best moment for the first feeding, the importance of colostrum, and nutritional aspects for nursing mothers require further clarification during prenatal care and the immediate post-partum period.