Background and purpose: As clear mechanisms for motivating and engaging teachers in learning and working collaboratively with colleagues are scarce, this study explored supportive conditions of promoting teacher professional development on inquiry-based science teaching in a Professional Learning Community (PLC) and examined how teachers' professional development impacted their students' learning outcomes. Design and methods: Two purposively selected lead teachers along with their PLC colleagues and students participated in this study. Results: The qualitative results reveal that the "interactive domain," in which PLC teachers work collaboratively in sharing teaching lessons and developing assessment items, plays a critical role in promoting their professional development. The quantitative results, indicating that the students of the two lead teachers outperformed their counterparts on scientific competencies, provide support that advancement of teachers' professional development is beneficial to student learning outcome. Conclusion: These results strengthen our understanding of the essential supportive conditions and mechanisms that an effective model must have for teachers' professional development, which can lead to better student learning outcomes.