Principals‟ training is crucial for the effective performance of their roles. Much of the training is sometimes done without doing a Training Needs Assessment (TNA) to find out exactly what the Principals need. This study, therefore, endeavored to identify the training needs of Principals in Kisii Count y. The low performance in examinations Kisii County may be an indication of compromised quality education due to poorly or inadequately trained Principals. The objectives of this study were: To identify the educational supervision competencies that secondary school Principals use and actually practice in the process of performing their supervisory roles, to identify the competencies that secondary school Principals need in order to effectively perform their educational activities in their schools, to determine the discrepancy between what supervisory competencies they need and those they practice and to develop a training model for the effective training of Principals in Kenya. The study used a mixed method approach design and within it used concurrent triangulation design.The study was guided by the Needs Assessment Theory. The study was done in Kisii County, which is one of the 47 counties in the country which register poor academic performance in national examinations in both primary and secondary schools. Kisii County is divided into 11 Sub-County administration units. This would make it ideal for the generation of adequate sample which would give reasonable data for analysis. The study population was the 11 Sub-County Directors of Education (SCDE), 11 Sub-County Quality Assurance and Standards Officers (QASOs), 11 TSC Sub-County Directors, 360 Chairpersons of Boards of Management of public secondary schools and 360 secondary school Principals in the County. Stratified, saturated and random sampling techniques was used to sample the respondents. A study sample of 99 respondents was used; 9 SCDEs, 9 SCQASOs, 9TSC Sub-County Directors, 36 Board of Management Chairpersons and 36 Principals. Questionnaires and interview guides were used for data collection. In order to ensure the validity of the instruments, two members of the school of Education, Humanities and Social Sciences of Jaramogi Oginga Odinga University of Science and Technology were contacted and their recommendations used to correct the final Instruments. Test retest method was used to ascertain the reliability of the research instruments. Quantitative data was analyzed using descriptive statistics and was presented in form of tables of frequencies where frequency counts, percentages, means and ranks. Qualitative data was analyzed using thematic analysis and then presented in themes and sub-themes that emerged during analysis. They were further presented in narratives, paraphrase and through verbatim reports. The following findings emerged from the study: The Principals‟ competencies in all the six areas studied were found to be average. Their in-service training programmes even though relevant were found to be untimely, inadequate, took very short time, and used methods and training materials which were not helpful. The INSETs were not based on any TNA results and no assessment of the impact of training on performance was ever done. The study also developed a training model for the training of Principals in Kenya. The study concluded that the training of Principals in Kenya is irregular and this has resulted in the Principals being averagely competent, a situation that might compromise their role performance. The study recommends that: Principals in Kisii County should be trained on the six competence areas identified; the Teachers Service Commission should include a Master's Degree in Education and a Post Graduate Diplo ma in supervision and quality management in education as part of the appointment criteria; the Ministry of Education should improve on the INSETs offered and always conduct TNA before any INSET programmes are conducted and the government should consider adopting the training model developed by this study to ensure that the training of Secondary Schools Principals is made better