This chapter examines the professional learning principles and practices enabled through the Teacher Learning and Leadership (TLLP). It describes the projects and goals that teachers set for their professional learning and discusses the activities they chose to participate in to reach those goals. The chapter provides evidence to demonstrate enormous value of the program for teachers' and their students' learning. It includes summaries of a selection of ten TLLP projects illustrating the nature and diversity of TLLP professional learning foci and activities. A key goal of TLLP is to support experienced teachers to undertake self-directed advanced professional development for improving their practices and supporting students' learning. Current research suggests that teacher professional development should be "job-embedded, ongoing and related to the challenges teachers face in daily classroom instruction". By far, the most common professional learning activity initiated and undertaken by TLLP participants was teacher collaborative learning. Participating in a TLLP project can yield significant benefits for teachers and their students.