Based on a case study of a faculty at a university in Hong Kong, this chapter examines how a grassroots approach to professional development enhances the capacity of the teaching staff for blended learning. Professional development plays a pivotal role in supporting the teaching staff to adopt blended learning in their courses to enhance the quality of learning and teaching. However, professional development policies and practices do not always meet the professional learning needs of staff, and many of them do not feel supported in their blended learning practices after attending the professional development sessions. This chapter first discusses how the grassroots approach to professional development in blended learning was developed and implemented in the faculty. Both qualitative and quantitative data were collected and analysed to document the impact of the professional development on staff’s adoption of blended learning in their courses. Based on the key findings from this set of data from the faculty, the grassroots approach is refined and customised for each faculty at the university as part of the scaling-up process. Copyright © 2021 Springer Nature Singapore Pte Ltd.