Self-disclosure occurs in clinical settings such as psychological counselling and mentor-mentee self-disclosure in the context of early career employment and influences the dyad relationship building. However, there is little research of self-disclosure in the dyad interactions in pre-service teachers’ field experience. Drawing on the data from six mentor-mentee pairs in the United States, this study explored mentor self-disclosure and examined the impacts on mentoring. Sense of belonging theories and mentors’ roles guided analysis of the findings, and highlight that mentors disclosed personal and professional experiences and shared the struggles and failures in their first-year teaching experiences, thereby helping pre-service teachers reduce stress and anxiety when challenged as teachers. Additionally, mentors provided emotional support, which helped pre-service teachers to develop a better understanding of teachers’ professional experiences and further develop a sense of belonging.