The purpose of this study was to explore nursing roles and nursing leadership in a breastfeeding promotion group. Eight key nursing staff participated in interviews. The results showed that servant-leadership strategies applied by key nursing staff included being self-confident, being empathetic, giving of themselves, being persuasive, being self-adjusted, and being authoritative, which are the characteristics of servant-leadership. Without the authority to make major decisions, these key nursing staff encountered difficulties, including cross-section and cross-grade communication, and organizational changes. In a doctor-dominant hospital culture, nurses using servant-leadership have successfully led breastfeeding promotion groups to win local accreditation for ”baby-friendly” hospitals, and have actually promoted breastfeeding. This study could be used as a source of reference in relation to the development of nursing leadership in a cross-professional group.