The purpose of this study was to evaluate the implementation of a change to the breastfeeding policy in seven hospitals in accordance with the 'Ten Steps to Successful Breastfeeding' issued by the World Health Organization and the United Nations Children's Fund and to assess the impact of hospital practices on breastfeeding. A 3-year quasi-experimental pre-post test design was conducted in 12 hospitals. The subjects were composed of 4614 lactating women in both experimental and control groups. The research instruments included the Baby-Friendly hospital Initiative training programs and questionnaires on breastfeeding duration, knowledge, attitude, and demographic data. Breastfeeding rates (including exclusive breastfeeding, mixed breastfeeding, and overall breastfeeding rates) of the experimental and control groups were measured and compared at four different times, during the hospital stay and at 2 weeks, 1 and 2 months postpartum. The results indicated that the exclusive and overall breastfeeding rates of the experimental group were higher than those of the control group (p < 0.001); moreover, the breastfeeding rates generally exhibited an increasing trend year by year ((p < 0.001). The results also showed that the experimental group scored higher in breastfeeding knowledge than the control group as did positive attitudes toward breastfeeding (t > 1.96, p < 0.05) with scores increasing year by year. The results also showed that higher scores reflected better knowledge in breastfeeding, and, in turn, a longer duration of breastfeeding.