Facilitators are central for the success of professional learning communities (PLCs). Yet, their specific roles in supporting teacher learning remain still largely underexplored. To address this gap, the current multiple case study examines the roles of 4 university PLC facilitators, the strategies they used to support teacher learning, and the challenges they experienced in their work. Data were collected through in-depth interviews and document analysis of facilitators' reflective journals and annual reports. Our findings revealed that the roles of PLC facilitators must continuously adapt to the needs of the community. Facilitators' tasks ranged from organizing group work and supporting community building to generating opportunities for teacher learning by stimulating reflection and by providing access to relevant resources and continuous feedback. Challenges associated with their roles included time limitations, the need to avoid the image of experts, and keeping a critical stance whilst building a close relationship with the PLC.