Background: Brucellosis is a zoonotic organism that causes diseases in both animals and humans. Human contact with infected domestic animals is often a transmission route of Brucellosis infection. This infection affects hematol. parameters of the patients. We carried this study to determine the changes in various hematol. parameters in our study subjects. Patients and Methodol.: This study was carried out in Nangarhar regional hospital and safi medical complex on 45 Afghani people from Dec. 2018 up to Dec. 2020. The study design was prospective. A total of 45 patients (Cases) with confirmed diagnosis of Brucellosis on the basis of serol. enrolled in the study. Complete blood count and Erythrocyte sedimentation rate studies are also performed. Considered hematol. parameters includes Hb (Hb), White Blood Cell count (WBC), Platelet count (PLT) and ESR. As well interview was done with each patient and a questionnaire was used. The collected data was analyzed with Microsoft excel program Autosum statistics. Results. A total of 45 patients were enrolled. The mean age±SD of the patients under the study were (28.74±15.22) years. The most common hematol. changes observed were; anemia (57.7%), thrombocytopenia (24%), leucocytosis (13.3%), pancytopenia (24.4%), lymphocytopenia (31.1%), lymphocytosis (55.5%) & leucopenia (40%). Erythrocyte sedimentation rate were elevated in about 66% of patients. Fever and headache were the most common presenting symptoms (73%) and (82%) resp. Night sweats in (40%), joint pain (53%), muscle pain (53%) and lymphadenopathy in 46% of patients. Conclusion: This result of this study shows that Brucellosis commonly affects people of low socioeconomical states, female sex, uneducated, those consuming contaminated dairy products, peoples living in rural areas and those having consuming or contact with animal. Salmonella typhi causes changes in the hematol. parameters due to involvement of bone marrow.