The purpose of this study was to establish the effect of resource allocation in strategic planning on school performance in Catholic Church owned Secondary Schools in Nairobi Archdiocese in Kenya. The study was anchored on Resource Based View theory. The study adopted Cross-sectional descriptive survey design since it allowed the researcher measure the outcome and the exposures in the study participants at the same time. Out of the different techniques in probability design, the study used stratified random sampling to select accessible population. It was used to divide the population of the study into two strata according to the two counties that form Nairobi Archdiocese (Kiambu and Nairobi city). The population for the study comprised of 24 schools with sample size of 8 schools through simple random technique. The data was collected using structured questionnaire and interview guides. The study used both descriptive and inferential statistics to analyze the data from the questionnaires using the Statistical Packages for Social Scientists (SPSS) program of version 23. Data presentation was through pie charts, tables and graphs. The study findings established that most principals are involved in supervision of teachers in their teaching and learning process and generally concerned about staff performance and attainment of school goals. Further, the study findings demonstrated that most of the schools studied did not have well equipped laboratories but had libraries with sufficient learning materials and adequate teaching and instructional materials and spacious classrooms accommodate students per class. It was recommended that, school boards of management should allocate more resources for the realization of schools strategies and therefore improve their performance. The study conclusively responded to the problem regarding resource allocations in strategic planning and the performance in Catholic Church Owned Secondary schools in Nairobi Archdiocese, Kenya. Key words: Resource allocation, strategic planning, school performance, Catholic Church