Complementing prevailingly outcome-oriented research on professional learning communities (PLCs), this paper focuses on conditions within school organizations that promote the communities work. Of prime interest is the predictive value of principals supportive leadership for variations of constitutive PLC elements and, furthermore, the specific features that characterize supportive leadership. To answer these questions, the theoretical part of the paper describes core dimensions of PLCs and potential approaches of targeted support by reviewing available classifications and empirical investigations. Our review reveals, among other things, that supportive leadership is not restricted to providing structural resources but also includes establishing trustful relationships, contributing ideas to instructional improvements, and sharing responsibilities. As expected, results from multilevel structural equation models (N=395 teachers) document significant associations between perceived leadership behaviours and core dimensions of professional communities among faculty staff, even though staff members ratings do not fully reflect the theoretically assumed distinction of four different facets of supportive leadership.