Background: Poultry by-products are a rich protein source that has the potential for recycling valuable products. Considering that poultry by-products are an important problem for the environment, it is necessary to find some ways to convert them into valuable products. Identifying and introducing microbial sources with the appropriate protease ability that can be used in the fermentation and conversion of non-useful waste into beneficial ones are highly important in medical and environmental terms. Objectives: The aim of the present study was to evaluate the antioxidant properties of fermented poultry by-products using proteolytic isolates. Materials and Methods: The samples were collected from a poultry slaughterhouse in Karaj, and proteolytic microorganisms were screened. Finally, two isolates (R and D) with proteolytic activity were selected for fermentation. The fermentation was performed on poultry by-products with 12.5% inoculation, 150 rpm, 1% D-glucose, and 37° C. The antioxidant activity was assessed on fermented poultry protein hydrolysates (FPPH) by some methods, such as scavenging free radicals and the ferric-reducing antioxidant power (FRAP) assay. Results: The results showed that after 24 hours of fermentation, FPPH by D with 37.7% degree of hydrolysis demonstrated 72.3% DPPH scavenging and 7.975 ± 0.36 µmol Fe (II)/L, and after 48 hours, fermented samples with 52.6% degree of hydrolysis represented 95.9% radical scavenging activity and 3.483 ± 0.28 µmol Fe (II)/L in the FRAP assay. In addition, after 24 hours of fermentation, FPPH by R with a 33.7% degree of hydrolysis illustrated 64% DPPH scavenging and 5.992 ± 0.28 µmol Fe (II)/L. After 48 hours, hydrolysates had a 54.4% degree of hydrolysis, and radical scavenging was calculated at 95.3% and 7.286 ± 0.39 µmol Fe (II)/L in the FRAP assay. Conclusion: Since poultry by-products are used for feeding, fermentation is a suitable way to improve the quality of feed.