Objective: To test the effect of a breastfeeding educational program for improving breastfeeding knowledge, attitudes, and beliefs of maternal/newborn nurses, and to improve their intentions to provide breastfeeding support to new mothers. Design: Quasi-experimental, pretest/posttest design. Setting: Maternity units of 13 hospitals located in midwestern and east coast states. Participants: Nine experimental and three control hospital sites resulted in a convenience sample size of 240 registered nurses (RNs); 206 RNs in the experimental sites and 34 RNs in the control sites. Methods: Participation in the experimental groups involved the completion of two questionnaires upon study entry and then again after completion of a self-study module. Participants in the control groups completed the two questionnaires twice with a 4- to 6-week interval between them without access to the self-study module. Main Outcome Measures: Nurses' breastfeeding knowledge, attitudes, beliefs, and intentions to support postpartum mothers who are breastfeeding. Results: Findings suggest that this educational strategy was effective in improving maternal/newborn nurses' breastfeeding knowledge, attitudes, and beliefs, and intentions to support breastfeeding mothers. Conclusion: This self-paced, study module, which is guided by an on-site, trained staff member, may be a cost-effective strategy for improving nurses' breastfeeding knowledge and support to new breastfeeding mothers. Nurses may find this type of teaching modality to be less intimidating than a structured classroom setting, and more desirable for their busy schedules. JOGNN, 39, 658-666; 2010. DOI: 10.1111/j.1552-6909.2010.01184.x