Study aimed at investigating causes of job satisfaction of High School Principals in Kirinyaga County, Kenya. It used mixed method design. Quantitative data was analysed by two tailed t-test and one way ANOVA with significance level at 0.05. Calculated t-values and F-ratios were compared with the critical values in order to reject or fail to reject the null hypothesis. Interviews and observations collaborated the study findings. Results indicated that Principals in Kirinyaga were not satisfied with their jobs. They were especially dissatisfied with job factors such as; remuneration, promotion and job security.Overall job satisfaction among Principals was very low. It was also established that there was no difference between job satisfaction among High School Principals and their gender. Still there was no significant difference between job satisfaction among High School Principals and the School's geographical location. Study recommended that the Ministry of Education considers reviewing remuneration as well as the scheme of service of Principals with a view to improving them. It is also recommended that the Ministry of Education review policies governing promotions of Principals