Public secondary schools in Kenya are expected to operate at affordable and sustainable costs. Despite this expectation, the cost of education in relative terms in most public secondary schools in Bomet County is still high. This may be an indicator that public schools are cost inefficient in their operations. The purpose of this study was to investigate the moderating influence of financial management skills on the influence of selected school characteristics on cost efficiency of public secondary schools in Bomet County, Kenya. The target population was two hundred and seventy principals of public secondary schools and all the five Sub-County Directors of Education in Bomet County. A sample of one hundred and seventy-five principals was selected using stratified and simple random sampling techniques. A semi-structured questionnaire was used to gather data from the principals and an interview schedule was used to solicit data from the Sub-county Directors of Education. The Content Validity Index was used to check for validity, and it found that all variables had an S-CVI of greater than 0.9, indicating that they were all valid and could be used in the study. All variables had Cronbach alpha coefficients of greater than 0.7, indicating that the variables were internally reliable enough to be used in the study. The data was analysed and summarized using descriptive statistics, such as frequencies, means, and standard deviations. To test the hypotheses, the researchers employed a moderated multiple linear regression analysis in inferential statistics to see how well financial management skills had a moderating effect on the influence of selected school characteristics on cost efficiency of public secondary schools in Bomet County, Kenya. Statistical operations on data analysis were performed using the Statistical Packages for Social Sciences (SPSS) statistics software. The study concluded that financial management skills did not have moderating influence on the relationship between selected school characteristics and cost efficiency of public secondary schools in Bomet County. This was linked to low financial management abilities of the stakeholders, which were characterized by poor financial mobilization skills of school alumni and school administrators. According to the study, the ministry of education should invest in capacity building for school administrators on financial management in order to improve cost efficiency in public secondary schools in Bomet County. School administrators, in particular, require capacity building in order to enhance skills on school resource mobilization. This could create appropriate resources to keep the schools running optimally in terms of cost.