One of the challenges in mentoring relationships is to understand the real issues faced by the mentees. A mechanism has been established to offer a credible mentoring inventory. The aim of the study was to determine the construct validity and reliability index of the Universiti Sains Malaysia Mentoring Inventory (USM-MT-i) among early phase medical students in a Malaysian public medical school. A cross-sectional study was conducted in June 2017 among 208 early phase of the medical students of School of Medical Sciences, Universiti Sains Malaysia. USM-MT-i is a self-administered inventory and was established based on the information gained from the mentors and mentees. The prevalidated inventory entailed 44 primary items. Exploratory factor analysis (EFA) and Cronbach’s alpha reliability analysis were utilised to determine the construct validity and reliability of such inventory. The result revealed three potential constructs with 39 items extracted from the USMMT- i; academic leadership (19 items), communication skills (12 items) and examination competence (8 items) with factor loading ranges from 0.50–0.77, 0.51–0.80 and 0.65–0.87, respectively. Internal consistency reliability (Cronbach’s alpha) for each domain were 0.95, 0.93 and 0.92, respectively. The overall Cronbach’s alpha was 0.96. The present study promoted that the three factors with 39 items of the USM-MT-i has a good validity and reliability value to survey for mentoring needs among medical students in their early phase.