The “Co-mentorship in the Educational Practicum” Course is a course which combines the concepts of team teaching and mentoring into the teaching practice. The teaching practice courses are jointly taught by the practicum course professors and the practicum course teachers. The teachers and the pre-service teachers form a mentoring relationship and, conduct this course on a mentoring basis. In this study, 41 pre-service teachers, six practicum course teachers, and two practicum course professors participated in the Co-mentorship in the Educational Practicum Course. This study summarized the operation model of the “Co-mentorship in the Educational Practicum” Course through semi-structured interviews and document analysis. It also investigated the professional growth of the pre-service teachers in this course. The results show that: 1. He internship course consists of two parts, in-classroom and out-of-classroom. The former establishes the basic concept, teaching preparation, reflection and review; while the latter offers three-cycle teaching and intensive practice. 2. The professional growth results of pre-service teachers in teaching skills are as follows. They understood that the teaching activities should map the teaching objectives and integrate students’ living experiences. In these activities, they were able to properly use various teaching skills, such as guided discussions, cooperative learning, communication, and teaching media, and then, analyze student learning outcomes through multi-evaluations. In terms of the professional growth of pre-service teachers in class management competency, they established appropriate class policies and set up reward systems. In addition, they learned the skills required to build good teacher-student relationship and to deal with emergencies through adaptive counseling. Therefore, the “Co-mentorship in the Educational Practicum” Course can indeed promote the professional development of pre-service teachers in both teaching skills and class management.