This study assessed the application of warning and reprimands by heads of schools on the management of professional misconduct among public secondary school teachers in Mara region, Tanzania. The reviewed literature indicated that there is a high rate of teachers' professional misconduct and there was need of assessing the application of warnings and reprimands and find a way that can be properly used to manage teachers' professional in the school environment. The study was guided by Transformation Leadership Theory which guides the HOSs to use different strategies in managing of teachers' professional misconduct including warning and reprimands. The study used mixed methods approach and the convergent mixed research design whereby quantitative and qualitative data sets were collected simultaneously. The target population involved 300 students, 138 teachers, 25 heads of schools and 5 District TSC Officers. Stratified, simple random and purposeful sampling techniques were used to determine the study sample that consisted of 468 respondents. Questionnaires, interview guides, interview schedule, and document analysis guide were used to collect the required data. The collected data were analyzed by descriptive and inferential statistics using independent t-test. Narrations and direct quotations were used to present qualitative the study findings. However, the study also revealed that there was a significant relationship between the level of application warnings and reprimands strategy and management of teachers' professional misconduct. The study concluded that warnings and reprimands were not properly applied due to unfairness, favouritism and insufficient of knowledge and skills by HOSs in dealing with management of teachers' professional misconduct. The study recommended that TSC under the government should give education to the heads of schools on the proper usage of warnings and reprimands to avoid favouritism to the teachers when issuing warnings and reprimands.