Mobile Banking service are created to help businesses streamline their operations and this, has received immense adoption in Kenya since it was introduces in the year 2007.The study's objective was to determine the magnitude to which small and medium enterprises have adopted mobile banking in Nairobi County, to establish the magnitude to which SMEs utilize the different services offered by the mobile banking and to establish the association between usage of m-banking services and SME performance. The study applied a descriptive type of survey design aimed at finding out effects of m-banking adoption on performance of SMEs in Nairobi County. The population targeted in this research study was 176 SMEs n Nairobi County. Primary data was collected. The study revealed that ease of use, cost effectiveness, convenience; security of the service, accessibility and diversity has enabled SMEs to continue to use mobile banking services. The study also revealed that mobile banking has increased customer base because of easy method of payments, more time to carry out other business activities, easy access to funds in the bank, increased business transactions, increased profits and increased business efficiency. The study made a conclusion that mobile banking adoption positively influences SME spar for mince in the county of Nairobi. The study recommended SMEs to adopt m-banking services in their organizations. In this way the organization will be adopting the changing technologies so that to remain competitive.