Transformational leadership is an ideal characteristic which enables the principals to engage with followers and raise consciousness about the significance of specific outcomes and new ways in which those outcomes might be achieved. The purpose of this study was to investigate the influence of principals’ intellectual stimulation on student academic performance in Kenya Certificate Secondary Examination (K.C.S.E) in Makueni County, Kenya. The objective that guided the study was to: assess how the principals’ intellectual stimulation influences students results at Kenya Certificate of Secondary Education. with the hypothesis that there is no relationship between principals’ intellectual stimulation with students’ mean scores at Kenya Certificate of Secondary Education Makueni County, Kenya. The study used transformational leadership theory by Burns (1978) which has four dimensions namely idealized influence, inspirational motivation, intellectual stimulation and individual consideration; all of which are critical in determining academic achievement. The conceptual framework of this study is based on the relationship between the principal transformational with academic performance. The sample comprised of 111 principals, 729 teachers and 12 Ministry of Education officials drawn from 388 secondary schools. Questionnaires and interview guide were used to collect data. Validation of the questionnaires were through test re-test method and use of expert judgment. The coefficient value was 0.85 at alpha = 0.05. Data was analysed using both descriptive Pearson’s correlation coefficient that test showed a strong correlation for Intellectual stimulation and KCSE students’ mean scores. The result indicated a negative and strong correlation between intellection stimulation and students’ KCSE performance (r=-.195, p-value<0.05) respectively. It was concluded that principals’ collective sense of mission and valuing ideas of the followers increased performance. The following recommendations were made: KEMI to carry out transformational leadership seminars for the principals on intellectual practices. The Ministry of Education Policy makers should establish policies on transformational leadership. Teacher trainers especially the universities ought to review curriculum to include analysis of school managers and also have simulated situations.