Invasion of animal's erythrocytes by Babesia parasites causes alteration in antioxidant potential of the red cells so this study was conducted to assess the effect of Babesiosis infection on some oxidative stress and antioxidant agent in calf naturally infected with Babesi where the study was carried on 70 fattening calves aged in 2-3 years, from different localities in New-Valley Governorate, Egypt. The animal under the study classified into three groups, group 3, include 40 fattening calves naturally infected by Babesia and ticks, group 2, include 15 fattening calves infected with ticks only and group 1, include 15 fattening calves clinically and laboratory healthy (control group). The parasitological diagnosis was confirmed by indirect fluorescent technique (IFT) and the diseased calves divided into 4 subgroups according to parasitiaemia rates (0.5%, 1%, 1.5%, 2%). The calves under the study were free from internal parasite by clinical and studies. The study revealed a significant increase in oxidative marker (NO and MDA) in the diseased group with Babesiosis than tick infected group and control group while the biochemical serum analysis for antioxidant markers revealed an highly significant decrease in all antioxidant parameters under study, SOD, GSH-R, Catalos, Ascorbic acid and TAA, as the fallowing values, 290.13±31.21, 2.01±0.92, 0.93±0.04, 99.75±2.47 and 0.83±0.32 respectively. The study indicated that the Babesiosis calves are at greater risk of oxidative damage than other groups studied, hence early diagnosis, treatment and addition of dietary antioxidants are highly encouraged and essential requests for improve of productivity of fattening calves.