This study sought to examine the impact of teachers‟ involvement in decision making in public secondary schools in Kahama town council. It examined the extent to which teachers participate in decision making and the approaches applied by the heads of schools in involving teachers in decision making. The study determined the impact of teachers‟ involvement in decision making in schools. The study used a research mixed approach and sequential explanatory design. A total number of 93 respondents were involved. They included teachers, academic coordinators and heads of secondary schools. The informative data were collected by using questionnaires, interviews and document reviews. Quantitative data were analyzed by using descriptive statistics with the assistance of SPSS version 22 while qualitative data employed thematic and content analysis. The study established that, in most public secondary schools heads of schools involve teachers in decision making processes to a reasonable extent. It was also revealed that, the heads of schools involve teachers in different areas of school daily activities, notably students‟ discipline, framing the timetable, handling of internal examinations and allocation of duties to teachers. Besides, it was confirmed that in most schools, the democratic approach was used. It was unveiled too that, the involvement of teachers in decision making has positive implications as opposed to the negative implications that one would expect. The study recommends that, the government should set up policies that require heads of schools to involve teachers in decision making. Furthermore, the study recommends that, the government should introduce a system of ensuring regular monitoring on practice employed by heads of schools in decision making in order to determine the extent to which teachers are involved in decision making.