Abstract: Competition is a factor that affects the business environment in any industry. This study sought to investigate the impact of competition on the performance of the mobile telecommunication industry in Kenya. This research aimed at looking at how competition has impacted on performance of the four firms in the sector i.e. Orange Kenya, Airtel, Yu and Safaricom (K) ltd. The study used a descriptive research design that answered questions how competition affects the independent variables of the study i.e. new market entrants, competitive rivalry and buyer power.