Mentoring programmes are cost effective for both novices and practicing secondary school teachers as when carried out earlier, become competent and confident. Yet, a few studies have been conducted in Tanzania in particular Mbeya region on the matter. The study examined the effectiveness of mentoring process in developing teaching competencies of the secondary school novice teachers in Mbeya region, Tanzania. Padua’s theory, Social cognitive theory and Herzberg two factor theories guided the study. Case study design with mixed approaches was used. A sample size of 110 novice and experienced teachers was administered with questionnaires and interview guide respectively. Descriptive statistics aided in analysing quantitative data while content analysis served for qualitative data. The findings revealed that mentoring programs resulted into confidence and command among novice teachers where mentors cultivate specific ideas among mentees in facilitating teaching and learning. Yet, mentoring programs contributed to the professional development of novice teachers with personal support to cope with their new work environment. It was concluded that mentorship effectively develops novice teachers’ competencies and recommended that mentors should cultivate further understanding of how to help novice teachers and how to create mentoring goals to support novice teachers’ progress in the beginning of their teaching career.