This paper examines a good practice for service learning that has been implemented for years in TESOL Internship, a professional unit for students doing Master of Arts (MA) in Teaching English to Speakers of Other Languages (TESOL) at a major university in Australia. The author has investigated and identified three key features of a good practice in service learning, including critical reflection, community engagement and intercultural communication, which are evidenced in student service learning in various English language centres in Great Western Sydney. Data are collected from student reports, supervising teachers’ reports and comments, weekly workshop discussions and emails. Using constructivist grounded theory (Glaser & Strauss, 1967), the author conducts thematic analysis to code the data, categorizes them into key themes for critical analysis. The results show that during their practicum period TESOL student teachers critically reflect on their observation experience and participate in curriculum-relevant and extra-curriculum activities, particularly their own teaching practices drawing on relevant TESOL theories and communicating with their peers and mentors. Furthermore they come to understand local communities better as they are actively engaged in interacting with members of local communities. Finally their intercultural awareness is enhanced through regular and active intercultural communication with people of diverse language and cultural backgrounds. Opportunities and challenges for good service learning practices are also discussed.