Abstract: The study focused on the informal micro retail sector in Nairobi researching on the enterprises in the Smart Duka project run by a Non-Governmental Organization and investigating the use of group participation and its effect on the financial performance of these enterprises which are located in the informal settlements of Nairobi. Prior studies have focused more on areas outside the informal sectors of Nairobi and have had limited focus on the effect of group participation on financial performance of enterprises which the current study sought to address. The financial performance and business factors of the enterprises that joined groups (treated group) were compared to financial performance and business factors of the enterprises that did not join groups (control group) in the project.