This study sought to establish the factors influencing the adoption of mobile banking in Nairobi County. The specific objectives of the study included establishing how the perceived ease of use, perceived risk, perceived usefulness and how social influence affects mobile banking adoption by bank customers. The research focused on 43 commercial banks with branches within Nairobi Central Business District and formed the population of the study. For each of the 43 banks in Nairobi the biggest in terms of customer size was chosen. The researcher randomly picked five respondents from the odd numbered banks that were 21, leading to a sample size of 110 respondents. The study was underpinned by the theories of adoption of technology and theories that support the adoption of mobile banking. The research design that was adopted was a descriptive and correlation research design. Primary data was collected through the use of a questionnaire with both closed and open ended questions. The descriptive analysis adopted, involved the use of tables, pie charts, percentages, mean and standard deviation to summarize the respondents‟ answers, and answer the four research questions. Results indicated that out of the four factors, perceived ease of use of mobile banking and social influence of mobile banking had a positive and statistically significant influence in adoption of mobile banking in Nairobi. On the other hand, perceived usefulness of mobile banking, and perceived risk of mobile banking were found to have positive and negative effects respectively but they both had a statistically non-significant influence on the adoption of mobile banking in Nairobi. The study recommends that financial institutions should invest in more easy to use technology as well as social innovations geared towards improving customer image in order to enhance mobile banking adoption in Nairobi County.