Objective: The study was conducted to determine the factors affecting breastfeeding success during early postpartum period among primiparous mothers who had a vaginal delivery. Method: The sample of this descriptive study, which was carried out at the birth clinic of a public hospital in Istanbul between June and July 2015 was composed of 278 primiparous mothers. The data were collected using a questionnaire prepared in line with the purpose of the study and the LATCH breastfeeding assessment scale. Numbers and percentage values were used during the analysis of the data. Findings: All of the mothers have been trained in the prenatal period about breastfeeding. Most of them had accurate knowledge and practices about breastfeeding and received information and breastfeeding support from midwives/nurses a few times during the postpartum period. The majority of the mothers who initiated breastfeeding at the hospital had problems during the first practice and needed help. After being discharged, almost all of them had worries about the continuation of breastfeeding and asked for breastfeeding consultancy during the postpartum period. The mean score of the mothers on the LATCH scale was 7.9 ± 1.46. Conclusion: It was seen that although the theoretical knowledge of the mothers about breastfeeding has been at a good level, this knowledge could not be turned into action. In order to initiate and maintain successful breastfeeding especially in primiparous mothers, in terms of their self-confidence, it is important to repeat practical breastfeeding training periodically and to inspect whether this acquired knowledge was put into practice