Many IT enterprises in Kenya face the challenge to improve data and voice services' competitiveness, quantity, quality and dependability. Strategic IT is seen as a critical aspect to solve these difficulties. The improvement of firm competitiveness does not always ensure that company performance is improved. The study's specific objectives were as follows; to determine the effect of system integration, system security, management support and data storage on performance of telecommunications firms in Nairobi City County. The study was guided by game theory, resource-based theory, system theory and Unified Theory of Acceptance and Use of Technology. The target population was 250 staffs of telecommunications firms in Nairobi City County, Kenya from different departments. The study employed a descriptive research methodology, with a sample size of 153 selected participants using a simple random selection procedure. Based on the regression coefficients results above, department integration has a significant effect (β=0.158; p<0.05) on performance of Telecommunication firms. It can be concluded that ERP capability offers system security by implementing user files whereby in order to log into the systems, one is required to input his or her password in order to gain access. Moreover, ERP capability ensures that all process storage is saved in system central database. The study recommended that the Nairobi County government and telecommunication firms commit sufficient resources to the implementation of an efficient and effective enterprise resource planning system and that automation be treated as a critical line of development in the telecommunications field.