The study sought to explore how school administrators applied andragogic principles to help erring teachers in selected public secondary schools in Lusaka District. The sample size was 30. The study was guided by Knowles ’s Theory of andragogy which holds the view that adults are self-directed and motivated hence expected to take full responsibility for decisions. A case study research design was employed. A case study enabled the researcher to gather in depth and detailed information about the subject which were a group of administrators on how they applied andragogical principles such as motivation, role of experience, self-directedness, need to know, readiness to learn and orientation to learning to help erring teachers in public secondary schools. As a result of using a case study, the qualitative approach was used. The qualitative case study afforded the researcher an opportunity to explore and describe the phenomenon in context using data obtained. The interview guide was used to collect data. Thematic analysis was used to analyze data. The study established that administrators demonstrated and appreciated that andragogical principles which included the role of motivation, experience, self-directedness, readiness to learning, orientation to learning and the need to know were inevitable in the learning and working of adults and helping erring teacher in secondary schools. However, administrators had inadequate knowledge on andragogical principles. Administrators agreed that they applied andragogical principles in their leadership practices in part. It was discovered that motivation and experience were applied regularly, self- directedness was applied to a certain extent in their leadership practices. The others like readiness to learn, orientation to learning and need to know were rarely applied or not applied at all due to inadequate knowledge on the principles by administrators. The study also revealed that Andragogical principles were necessary in leadership practices as they promoted high productivity and facilitated the creation of good working environments in secondary schools thereby helping erring teachers. Based on the constructivism view point, it was recommended that Universities and Colleges of Education should integrate andragogical principles in teacher training programmes with the help of the department of Continuing Education and Lifelong Learning (CELL) at the University of Zambia. Additionally, Administrators should be transformational in their leadership practices to help erring teachers in secondary schools through the application of andragogical principles which include the role of motivation, the role of experience, self-directedness, readiness to learning, orientation to learning and the need to know. Andragogical principles resonate well transformational leadership in that both concepts help in building trust between leaders and followers.