Workforce diversity is still thought of as an abstract concept that still requires further investigation in various sectors. It is full of mixed results on whether it impact on organizational performance or it is just a legal requirement. This study sought to evaluate the perceived influence of workforce diversity on organizational performance among international non-governmental organizations in Kisumu County, Kenya. The study was grounded on four research questions. The study adopted both descriptive-correlation research design in answering the four research questions. The data was collected through closed-ended questionnaires, built on a five likert scale. The study population consisted of 40 international non-governmental organizations that operate in Kisumu County, Kenya. Data was analysed using the SPSS computer software version 22.0. Frequency, percentages, mean and standard deviation was used to describe and summarize the data. Correlation analysis was sought to establish the relationship between of workforce diversity and productivity of International Non-Governmental Organizations. The findings revealed mixed results that, there is a statistically significant relationship between education diversity, professional networks and employee effectiveness which was used as a measure of organizational performance. Further findings revealed that there is no statistically significant relationship between workforce diversity (gender, age, ethnic, education and professional networks) and organization efficiency which was also used as a measure of organizational performance among INGOs. The study concluded that workforce diversity is perceived to influence organizational performance. The study recommends that management should come up will policies that will enhance workforce diversity in International Non-Governmental Organizations.