This study investigated the relationship between Top Management Team (TMT) demographic diversities and firm performance using generic strategies as intervening variable in the Marketing and Social Research Association (MSRA) firms in Kenya. First, the relationship between TMT characteristics diversities and generic strategy was analyzed. Second, the link between generic strategy and firm performance was estimated. Mixed methods research design was used to critically investigate the relationship between the latent exogenous and endogenous variables of this study. The mixed research design used in this study was triangulation design, which was mainly transformation design model. The data were analyzed using structural equation modeling analysis, using IBM SPSS AMOS version 21. The study found out that the homogenous demographic diversities among the top management team members had statistically significant effect on cost leadership strategy (p = 0.012). Besides, cost leadership strategy showed a statistically significant positive relationship on firm performance (p = 0.005). The findings of this study implied that organizations need to know and develop the best composition of top management team based on their demographic diversities in relation to the environment. Besides, the organizations need to empower the TMT members using monetary and nonmonetary incentives to further improve performance. Last but not least, the compositions of TMT in marketing research firms need to embrace gender diversity.