Based on the agency theory and the social exchange theory, the study determined the relationship between trust in knowledge sharing and business innovation in franchised fast food outlets in Nairobi City County. The significance of the study is to motivate single unit owners to join franchises, and help franchisees and franchisors reap the benefits of sharing knowledge to create competitiveness by embracing and sharing innovation. Target population was selected franchised fast-food outlets in Nairobi City County. A mix of descriptive research design and exploratory research was applied in conducting the study. Multistage sampling was used to select franchises and the sample was then distributed proportionally across each brand. The sample size was 180 staff from the 60 selected fast-food outlets in Nairobi City County. Data was collected through Interviews and questionnaires. Data was analyzed through inferential statistics such as regression analysis and Pearson correlation. The correlation analysis between trust and knowledge sharing showed that, trust is positively and significantly correlated to knowledge sharing in franchise outlets as indicated by 0.372 while p value 0.00 which is less than 0.05.The regression analysis between trust and knowledge sharing resulted to an R2coefficient of 0.138, which indicated that, there is a relationship between trust and knowledge sharing in franchised outlets. Further determination of variance was also performed; the findings indicated that, there was a significant effect between trust and knowledge sharing in franchised outlets. The p value was at 0.000 which is less than the p value of 0.05.