Workforce diversity is a multi-faceted phenomenon that will continue to evolve as the world becomes a global marketplace. No doubt many believe workforce diversity is fundamental for employee performance. This study sought to find out the effect of workforce diversity on employee work performance, using the MEKAB plc. In the context of this study the term workforce diversity was defined as the similarities and differences among employees in terms of ethnic background, gender and education. These similarities and differences formed the independent variables of this study. Literature review was done and an attempt was made to link the various published studies with this study with a view to discovering how each variable effect on employee work performance at the MEKAB. The most unfortunate is that there are no Work force Diversity (WFD) related studies done in Ethiopian context to the knowledge of the researcher. So the purpose of this study was twofold. The primary goal was to fill the research gap on the area in Ethiopian context by examining work force diversity practices of Case Study Affiliate Company and its effect on employee performance. To achieve the objective of the thesis, the research method used was explanatory survey design study. Through the use of primary and secondary data sources, the researcher has gathered the necessary information regarding WFD practices of the case study company MEKAB PLC and its effect on employee’s performance besides intensive literature review to identify gapes and different scholars point of view on WFD and demographic diversity model. The data collected from primary sources were analyzed quantitatively (using descriptive inferential method of analysis).The summarized responses were used to examine the effect of each variable on employee work performance. Correlation Coefficient analysis showed a significant level of association between performance and the tested variables of diversity. It became evident that workforce diversity has significant correlation between gender and employee performance the finding of this study showed gender, ethnic and employee performance is positively linked and education diversity has no significant effect on work performance of the employee. This study could be a guideline for future studies. It is therefore important for the institution to realize the need to capitalize on these demographic categories in order to stay ahead of other company or organization.