Getting knowledge of new technology developments to enhance food goods is becoming more popular. Nowadays, natural preservatives such as probiotics are preferred over chemical ones by all parties involved in food safety. Chemical preservatives have been shown to have numerous negative effects on food ingredients and human health. This study was conducted to investigate the antimicrobial effect of two probiotic strains (Lactobacillus acidophilus and Bifidobacterium lactis) alone against Staph. aureus and E. coli growth in chilled fresh tilapia fillet samples (that were previously irradiated with UVR to ensure that the samples were free of target microorganisms) during storage at 4°C for 8 days. The results showed that Lactobacillus acidophilus had almost the same effect as Bifidobacterium lactis in reducing Staph. aureus. However, Bifidobacterium lactis was more effective than Lactobacillus acidophilus in reducing S. aureus count. Moreover, the growth of S. aureus continued until the 6^th day of storage, with complete inhibition done on the 8^th day. In addition, Bifidobacterium lactis was more effective than Lactobacillus acidophilus in reducing E. coli count. Overall, E. coli was able to persist in the presence of both probiotics until the end of the experimental period. The maximum reduction in E. coli counts reached 0.806 log10cfu/g (47.17%) by using Bifidobacterium lactis. Therefore, it is recommended to use probiotics as one of the biological preservation systems for foods against Staph. aureus and E. coli.