The effect of different concentrations of sodium tripolyphosphate on the bacteriological quality of refrigerated Nile tilapia fillets was determined. There were significant differences (P<0.05) among control with different concentrations of STPP treated samples on Total Aerobic plate count (APC) and the psychrotrophic bacteria counts. The control and 2%STPP treated samples exceeds the maximum permissible limit 6 log of APC after 6th and 9th day, respectively. While both 5%STPP and 10%STPP treated samples exceeds this limit after 12th day. Non-significant differences (P>0.05) were detected among all examined samples at 0 day, 3rd, 6th or at 15th day on total coliform count. The highest reduction % of APC, total psychrotrophic count and total coliform count was (26.62% at the 3rd day, 32.99% at the 9th day and 20% at the 6th day) of 10% STPP treated samples, respectively. This study shows that, STPP have anti-microbial effect on APC and psychrophilic count but it has no effect on coliform bacteria. And it helps in extension of Nile tilapia fillets shelf life during refrigeration storage.