This study is based on the exploration of a mentor's and a mentee's perceptions about the process of mentoring as a tool for the professional development of novice teachers. The novice teachers find it difficult to adjust in a new school due to lack of experiences and unfamiliarity with the school culture. At this stage, a beginner teacher needs support and guidance of the senior/experienced teachers in order to overcome the initial days' challenges of teaching and learning in the school. Mentoring could be introduced as an in-service professional development course, to guide and support the novice teachers in the school. During mentoring an experienced and expert teacher helps the beginner teachers to teach in a better way. To know about the effectiveness of the mentoring process in the professional development of teachers, a qualitative case study was carried out with a mentor and a mentee to explore their perceptions about the process of mentoring as a tool for the professional development of teachers in one of the private schools in Karachi. The findings revealed that mentoring contributed significantly in the professional development of beginner teachers by developing their pedagogical as well as content knowledge. Both mentor and the mentee perceived mentoring as being more beneficial, as compared to other professional development courses, because it provided them field-based support and guidance. The research findings show that time constraints, checking of lesson plans, observation/feedback, and the development of reflective skills were the major challenges faced by the mentor and mentee during the process of mentoring. The data suggests that allocating quality time and providing opportunities for mentors to be exposed to different trainings and courses could enhance the effectiveness of the mentoring process further.