The objective of the study was to establish the effect of competitive intensity on performance of private security firms in Kenya. The data was collected from key informants who were either the marketing manager or the Chief Executive Officer of the firms. The theoretical foundation of the study was based on the Market Based View which provided theoretical perspectives on how external environmental factors including competitive rivalry in the industry can influence firm performance. The study was cross-sectional in nature and it targeted 39 firms that were members of the Kenya Security Industry Association (KSIA). A census was done because the population was relatively small. A total of 37 firms participated in the study and this translated to a 95% response rate. Data was collected from the respondents using a structured questionnaire whose measurement scales met all the requirements of reliability and validity tests. Descriptive statistics were used to gain a good understanding of the respondent and firm characteristics. Simple linear regression was used to establish the effect of competitive intensity on firm performance. Results of the regression analysis indicated that competitive intensity had a positive and significant effect on non-financial performance of private security firms. The study concluded based on the results of the regression analysis that competitive intensity has a positive and significant effect on the non-financial performance of private security firms in Kenya. It recommended that the management of private security firms and other firms operating in industries where the industry rivalry is high should be proactive and adopt a competitor orientation in their firms by monitoring the strengths and weaknesses of competitors and anticipating competitor actions that may affect the firm. However, the study also recommended that the firms should not be too competitor oriented otherwise they may lose their focus on customer needs and this may be detrimental to firm performance. Future studies should investigate the influence of government regulation on the relationship between competitive intensity and firm performance. This study was quantitative in nature and future studies should consider using qualitative approaches to data collection and analysis to establish if the findings will be similar.