The present experiment was conducted to evaluate the effect of dietary inclusion of quinoa seeds extract (QSE) as a natural antioxidant on broiler chicken performance, economical efficiency, meat quality and oxidative parameters of chickens' meat under refrigerated storage conditions. The extract was prepared and subjected to different analysis prior to use in broiler diets. A total number of 135 one-day old chickens of Ross strain were randomly allotted to three dietary treatments and each treatment contained 45 birds of 3 replicates each. The control group was fed a basal diet without supplementation while QSE was supplemented at a rate of 10 and 30 g/100 Kg diet to compose the other two experimental diets (T1 and T2), respectively. The results showed that QSE contains several phytochemical compounds with potential antioxidant activity. Those results were further confirmed by determining the total antioxidant capacity, total phenolic content and the radical scavenging activity of the extract. The dietary inclusion of QSE in broilers' diet showed that group T2 had significantly (p<0.05) higher body weight, weight gain and feed intake compared to T1 and control group. The proximate analysis results of chickens' meat showed that breast and thigh meat of the chickens in treatment T2 recorded significantly (p<0.05) higher protein content as compared to the other two groups. Regarding the antioxidant properties, the addition of quinoa seeds extract in broilers' diet resulted in a significant (p<0.05) improvement of the antioxidative properties of chicken meat. The oxidative stability of chicken meat under refrigerated storage conditions was evaluated at different storage days (1, 4 and 7) and it was shown that the dietary addition of QSE into broilers' diet succeeded in delaying the lipid oxidation of broilers' meat up to 7 days of refrigerated storage. The chicken meat of groups T1 and T2 showed no significant (p>0.05) reduction in their free radical scavenging activities at day 7 of storage compared to control group. From the present study, it can be concluded that the dietary inclusion of quinoa seeds extract in broilers' diet as a natural antioxidant have a positive effect on broilers performance, meat quality and also improved the chicken meat oxidative stability during refrigerated storage up to 7 days.