Despite significant roles played by Principals including instilling student discipline, learning institutions in Kenya, especially public secondary schools, have been faced with different cases of unrest emanating from students, teachers, and other staff members. Oyaro (2005) maintained that each school in Kenya has its own unique way of maintaining discipline in the student. The purpose of this study was to investigate perspectives on effects of Principals’ leadership styles on student discipline in public secondary schools in Vihiga Sub-County, Kenya. Objectives that guided the study were: to find out perspectives on effects of Principals’ transactional, transformational, laisserfaire leadership style on student discipline in public secondary schools; to establish perspectives on effects of Principals’ leadership styles on strategies used in instilling students discipline in public secondary schools. A descriptive research design was used and was informed by Social learning theory as well as Systems theory. The target population was 27 Principals, 321 teachers, and 3083 form three students from 27 public secondary schools in Vihiga Sub-County. A sample size of 431 participants was sought using simple random sampling (89% Principals,10% form three students and30% teachers). Data was collected using questionnaires and interviews. Reliability was determined through test-retest method and calculated using Pearson’s(r) giving an index of 0.820. Quantitative data was analysed using descriptive statistics and inferential statistics, and the qualitative data was analysed using thematic analysis. SPSS version 22.0 assisted in analysis of descriptive statistics. Findings of the study showed that there was statistically positive correlation between Principals’ transactional leadership and student discipline (n=289; r = 0.605; p<0.05);transactional leadership style explains about 36% of the variability in student discipline.There was statistically positive correlation between the level of Principals’ transformational leadership style and student discipline (n=289; r = 0.510; p<0.05); transformational leadership style explains about 26% of the variability in student discipline. There was statistically significant, though negative, correlation between the level of Principals’ laissez-faire leadership style and student discipline (n=289; r= -0.463; p<0.05); laissez faire leadership style explains about 21% of the variability in student discipline. The multiple correlation coefficients, R, between the three leadership styles and the dependent variable, student discipline was 0.899. Therefore, the independent variables explained 80.5 % variability in student discipline. The study concluded that Principals leadership styles are critical in instilling student discipline in Vihiga Sub-County. The result of the study established that varied strategies existed in instilling student discipline in secondary schools in Vihiga Sub-County, based on Principals’ leadership style. For instance, 58.8% of the students and 56.2% of teachers indicated that their Principal usually talks about his/her most important values and beliefs, as a strategy of preventing deviant behaviour. The study would assist the policy makers in the Ministry of Education to formulate viable policies on the handling of student discipline. The study would be useful to teachers, students, parents, and guardians in secondary schools. A study on perspectives of effects of Principals’ leadership styles on student discipline in private secondary schools in Vihiga SubCounty- Kenya would expound the understanding of the current problem.