This research study aimed to investigate the link between teachers' motivation levels and students' academic performance in secondary schools located in Mbarara City, Uganda. The motivation and commitment of teachers is widely recognized as crucial for the efficacy of teaching and learning processes in schools. Demotivated educators tend to provide substandard education which constrains students' ability to achieve optimal learning outcomes. The study sought to establish the factors demotivating teachers in Mbarara City secondary schools and how this impacts students' examination results. A mixed research design utilizing both qualitative and quantitative approaches was employed for the study. The target population included all teachers and students from 10 randomly selected public and private secondary schools in Mbarara City. Primary data was gathered through questionnaires administered to 374 teachers. Documentary review of students' past national examination records from the schools also provided key quantitative data. Data analysis revealed several interlinked challenges demotivating teachers including inadequate pay, lack of promotion structures, poor working conditions, heavy workloads, minimal participation in decision making and lack of acknowledgement for work done. All these negatively influenced teachers' level of dedication, effectiveness, expectations of learners and overall morale in work. Students of more motivated teachers reported having a favorable learning environment with invested educators who believed in their abilities. The findings clearly indicated a strong relationship between teachers' motivation levels and students' academic performance. Schools with demotivated teachers registered persistently low passing rates averaging 30-40% over the last five years compared to over 60% in schools with motivated staff. Demotivation of educators was found to severely curtail students' ability to achieve optimal results by compromising the teaching-learning interactions.