Security service delivery in public sector is crucial as it entails protecting government personnel as well as property. Therefore, security is increasingly viewed as a key condition for economic growth and development. Lack or ineffective security service delivery weakens the performance of any organization. This study sought to determine if service delivery improves as a result of outsourcing of security services to commercial state owned enterprises in Kenya. Specifically, this research aimed at determining the effects of outsourcing cash protection, body guarding, property protection and information/data protection services on security service delivery of selected commercial state owned enterprises in Nairobi City County in Kenya. The study was guided by two theories; the Functionalist model and securitization theory. A descriptive research design was adopted. The target population for this study was a census of all the 29 selected commercial state owned enterprises. The study targeted security managers, assistant security managers and security staff, hence total target population was 958 respondents. The sample size was selected through purposive and random sampling techniques. The research used questionnaires to collect data. Descriptive statistics including frequencies, percentages, means and standard deviations were used. Further, inferential statistics including correlation and regression analysis were used to illustrate the relationship between the independent and the dependent variables. The study used a multiple regression model. The regression results indicated that, there is a positive and significant relationship between outsourcing cash protection security services and security service delivery of commercial state owned enterprises in Kenya (β=0.247, p=0.001); a positive and significant relationship between outsourcing bodyguard security services and security service delivery of commercial state owned enterprises in Kenya (β=0.271, p=0.000); a positive and significant relationship between outsourcing property guarding security services and security service delivery of commercial state owned enterprises in Kenya (β=0.289, p=0.033); and a positive and significant relationship between outsourcing information security services and security service delivery of commercial state owned enterprises in Kenya(β=0.389, p=0.015). From the findings, the study concluded that outsourcing security services has a significant influence on security service delivery of commercial state owned enterprises in Nairobi City County, Kenya. In particular, the study concluded that outsourcing cash protection, body guarding services, property guarding and information security services, had a positive and significant effect on security service delivery of commercial state owned enterprises in Kenya. The study recommended that commercial state owned enterprises should strengthen their cash protection security services, security officers should be trained on how to protect human life especially, the personnel that they are supposed to protect, private security companies should keep data on any property that enters and leaves the company’s premises, and that private data security officers should have access to IT skills. This is an open-access article, access, citation and distribution of this article is allowed with full recognition of the authors and the source.  This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.