Bovine babesiosis is caused by the tick-borne blood parasite, Babesia bovis (B.bovis) and Babesia bigemina (B.bigemina). Many studies from 1980's to 2015's revealed that annual incidence of disease in summer season especially in adult cattle has associated with considerable economic losses. The present study were made on 115 Holstein calves at period from November 2014 till January 2015. Clinically affected calves showed signs of babesiosis as fever (41c°), anorexia, depression, weakness, pale mucous membrane, emaciation, weight loss, hematuria with accelerated heart and respiratory rates. Parasitological examination using Giemsa-stained thin blood films revealed presence of B. bovis in 54 out of 115 of examined calves while molecular examination by using regular Polymerase Chain Reaction (PCR) technique for same calves showed positive cases in 66 out of 115 and 14 out of 20 groups, Boophilus annulatus (B. annulatus) samples that affect these calves. There was a significant decrease in erythrocytic count, hemoglobin content, packed cell volume, albumin, globulin and total protein but significant increase in serum bilirubine in clinically affected cases of Babesia bovis. Pathological examination of liver and spleen showed golden yellow to brown hemosiderine pigment with inflammatory cells infiltration. In conclusion, the present study indicates that the change of some epidemiological aspects of clinical disease as age and season could be occure. Infected cases can occur at any time of the year in young calves less than three months. It could be occure in winter season, in contrast to some previous studies.