Performance of employees in any organization is one of the major determinants of profitability and sustainability. In any organization employees are major assets, they play a major role towards the organizations' success. There is the need for research to focus on the determinants of productivity and performance of employees in organizations. Career Advancement is many at times used to narrow the gap between the current performance and future expected performance. Empirical studies reveal that there is little research carried out on the link between career Advancement and employee performance in educational institutions. After the initial training many employees in Catholic Church managed schools have undertaken other trainings but have not moved up the ladder; rather they have stagnated at the same position with no or little to show in terms of career advancement. Catholic Church managed schools require employees who perform their duties well yet there is little to show in terms of promotions, students‟ results and advancement in these schools; lack of career advancement in these schools is still a problem. This paper presents a study on the effect of career advancement on employee performance in Catholic Church managed secondary schools in Meru Diocese Kenya. It adopts a descriptive research design since the researcher gathered both qualitative and quantitative data that describes the effect of career advancement in Catholic Church managed high schools in Meru Diocese. The target population includes all the 481 employees of all the Catholic Church managed high schools in Meru Diocese; this includes both the teaching and non-teaching staff.