This study was conducted to explore leadership mentoring practices and school climate in Seventh-day Adventist (SDA) schools in Southern Tanzania Union Mission (STUM). Concurrent triangulation design and descriptive-correlational study design with a cross-sectional data collection method were used. Variables involved in the study were leadership career development practices, psychosocial and emotional support practices, social relationships, school culture and transformational leadership style. The study took a form of a survey whereby 6 schools, 76 teachers and 5 heads of schools were involved, making a total of 81 respondents. Questionnaire and interviews were used to acquire data from respondents. Data was analyzed using descriptive statistics, Pearson product-moment correlation coefficient, multiple regression analysis and content analysis method along emerging themes and sub themes. Findings indicated that in SDA schools in STUM leadership mentoring practices are exercised at an average extent and the school climate is good in terms of social relationships, school culture and transformational leadership. There is a significant relationship between school climate and leadership mentoring practices. Transformational leadership style and social relationships are indicators that best determine leadership mentoring practices. Findings also indicate that lack of strategic leadership succession plans and leadership development and promotion policies are challenges affecting leadership mentoring implementation in SDA schools in STUM. The study recommends that heads of schools should maintain better social relationships, school culture and practices of transformational leadership style. School Boards should ensure that strategic leadership succession plans and policies are developed and implemented to guide the preparation and promotion of leaders in schools guided by the recommended mentoring action plan.