This study examined the influence of principals’ transformative leadership traits on the performance in science subjects in girls’ public secondary schools in Tharaka Nithi County, Kenya. It was guided by the following specific objectives: to ascertain whether principal-teacher role modelling influences performance in science subjects and to find out the relationship between the provision of supportive learning resources and the performance in science subjects in girls’ public secondary schools in Tharaka Nithi County, Kenya. The study was guided by transformational leadership theory. A concurrent triangulation design was adopted. The sample size for the study constituted 11 principals, 1 county director, 330 students and 100 teachers. The study used questionnaires to collect data from teachers and students, while interviews were conducted with principals and the County Director of education. Quantitative data was analysed using the Statistical Package for the Social Sciences (SPSS) version 25. The data from quantitative instruments was presented using frequencies and%ages on tables, graphs, and pie charts. Qualitative data was analysed in themes, and the reporting was done in direct quotations and narratives. The results revealed that the transformational leadership of principals, as evidenced by their role modelling for teachers and the provision of supportive learning resources, plays a crucial role in shaping the academic performance of students in science subjects within girls’ public secondary schools in Tharaka Nithi County. The study’s findings led to the conclusion that school principals are not consistently able to converse with and uplift girls facing difficulties in science subjects. Additionally, it was concluded that students lack adequate resources necessary for excelling in science subjects, notably the insufficiency of laboratory equipment, which has consequently impeded their performance in these subjects. The study recommended that principals actively engage and motivate girls to pursue science subjects. Additionally, it proposes that the government should focus on maintaining well-equipped and modern school science laboratories, providing science books in libraries, and offering online resources, educational apps, and e-learning platforms. These measures would supplement traditional teaching methods, creating a more interactive learning experience and ultimately boosting girls’ engagement and success in science subjects.