The general objective of this study was to evaluate the effect of management practices on organizational effectiveness in relation to SMEs in Kenya. Specifically, this study assessed planning, organizing, staffing and controlling as a strategic tool for organizational effectiveness in relation to SMEs in Nairobi County, Kenya. A review of various theories and conceptual framework, an understanding of management practices on through an in-depth analysis of empirical literature as well as linkages between the four variables and synthesis of literature and research gap analysis was undertaken. The study undertook a descriptive research design. The target population in this study comprised of all small and medium enterprises registered with Nairobi Municipal Council and operating in Nairobi County. Municipal Council of Nairobi d registered 34,242 SME's (Municipal Council of Nairobi 2015, Business activity code summary). The unit of inquiry was managers/owners of the firms. A sample of 340 SME's was selected from the list of registered businesses operating within Nairobi County, obtained from Municipal Council of Nairobi. Proportional allocation was used to determine the sample size from each stratum. Primary data was collected through a survey questionnaire. Document analysis involved reviewing the contents of target documents with the aim of adducing some relevant secondary data. The questionnaires were pre-tested in two SMEs outside Nairobi CBD to ensure that the instrument was reliable. Statistical Package for Social Science (SPSS) V.20 was used to analyze data using descriptive statistics. All the measures of central tendency and measures of dispersion were used. Data was then presented by way of tables and figures. Additionally, multiple regression was done to explore the association between different elements in a variable, and association between variables. The study established that management practices as strategic tools have a significant impact on organizational effectiveness of SMEs in Nairobi County, Kenya. Specifically, planning, organizing, staffing and controlling explain 70.8 percent of the variance in organization effectiveness.