The purpose of this study was to determine the controlling effect of firm size on the relationship between interest rate risk and value of the firm among Saccos in Kenya. The study was anchored on positivism research philosophy and utilised descriptive research design to determine the relationship. The study targeted all the 164 licenced SACCOs in Kenya. A sample made up of 115 respondents was selected using stratified random sampling method. The study utilized secondary data obtained from organization’s published financial statements. Data analysis of was done using inferential analysis (correlation analysis and panel regression analysis). R2 was used determine the predictive power of the model, F-statistic was used to test the fitness of the model while Pvalues were used to test whether there is any significant relationship between interest rate risk and the firm value of Saccos in Kenya as well as the controlling effect of firm size on the relationship. Study results showed that a positive significant relationship existed between interest rate risk and value of the firm (r=0.1827; P=0.0002<0.05). Results also showed that a positive significant relationship existed between firm size and value of the firm (r=0.0905; P=0.0000<0.05). Further, it was established that interest rate risk had a significant positive effect on value of Saccos in Kenya (β=0.22576, P=0.000<0.05). Firm size had no significant controlling effect on the relationship between interest rate risk and value of Saccos in Kenya (β=0.307521, P=0.000<0.05). the study Therefore concluded that Firm size had no significant controlling effect on the relationship between interest rate risk and value of Saccos in Kenya.