To manage, minimize and eliminate the challenges facing contemporary societies in the 21st century a multi-sectoral approach is required. For this to bear fruits all stakeholders must play their role as individual, communities, community based organizations (CBOs) among others. To contribute to the achievement of its objectives and social objectives, every organization has to employ strategies or approaches that enhance their performance. In line with this, many civil society organizations (CSOs) including CBOs have been applying Strategic Social Marketing approach to achieve their objectives. Although this approach has been in existence for a decade, there is an apparent lack of substantial empirical evidence on the impact of strategic social marketing on efficiency of community based organizations in the African context particularly in Kenya. This study investigated effect of strategic social marketing on efficiency of Community Based HIV and AIDs organizations (CBOs) in Nairobi County, Kenya. The study was guided by positivistic research philosophy. A cross-sectional survey research design was employed. The population of the CBOs comprised 350 organizations and area sampling technique was used. A sample of 183 CBOs was used in this study from eight constituencies which were proportionately represented. Random sampling was used to select sample elements. Descriptive statistics were used to profile characteristics of the surveyed organizations and the respondents. Correlation and multiple regression analyses were used to evaluate the relationships between strategic social marketing and efficiency as well as to assess its effect