The purpose of this study is to explore how participating in professional learning communities influenced teachers' curriculum design skills during the recent curriculum reform in Taiwan. A cohort of high school teachers in suburban areas participated in a semester-long professional learning community, strictly based on a well-planned agenda as professional experimentation. The researchers adopted a qualitative method by devising an initial and a final interview protocol as a data collection instrument. The results identified four components during the PLC process leading to teacher change in the curriculum design process--active participation, consistent focus, supportive collaboration and collective learning and shared practice. The notions of hard and soft PLCs along with the implications are proposed.