For a long time, there has been a tradition in China of experienced teachers helping beginning teachers. This empirical school study investigates the kinds of support that are provided by eight dyads of mentoring teacher and first-year secondary school teachers in Guangzhou of southern China and the major factors affecting mentoring support. In addition, this research focuses on the professional development of first-year teachers in areas of subject knowledge, student, teaching and classroom management. The findings reveal that mentors provide four forms of support: provision of information, mutual lesson observation, collaborative lesson preparation and discussion in the office. Factors affecting mentoring support include teaching workload, grade and subject, style of mentor-protege interactions, relationships between mentor and mentee, incentives for the mentors, and collegial culture in the case study schools. It is notable that there are positive and negative developments perceived by the protege and the foci of mentoring tend to be the teaching of content rather than curriculum and pedagogy. (Contains 2 tables.)