Background: Persons with hepatitis C virus (HCV) who are co-infected with hepatitis B virus (HBV) may be at risk for reactivation of HBV infection during or following HCV treatment. HBV and HCV share similar modes of transmission, and co-infection with the two viruses does occur. Objectives: This study aimed to evaluate the effect of HCV anti-viral treatment (DAAS) on HBV in HCV and HBV Coinfected patients. Patients and methods: The study was performed in Internal Medicine Department (Outpatient Clinic and the Inpatient Ward), Mahalla Hepatology Teaching Hospital, Gharbia, Egypt during the period from August 2016 to November 2017 on 20 HCV and HBV co-infected patients ranged from 18-70 years old. Results: The age of patients ranging from 26 to 65 years old (median 44). Male represent 55% and female represent 45% which showed male predominance. Patients were treated by different types by Hcv antiviral treatment (DAAS) like (SOF+DAC), (SOF+SIM), (SOF+DAC+RBV). At baseline, 12 patients had detectable HBV viral load, 5 Patients had positive (HBsAg) and undetectable HBV viral load and 3 patients had negative (HBsAg) and undetectable HBV viral load. Total number of HBV reactivated cases were 12 patients, 3 of them reactivated by increasing HBV DNA, and 5 of them reactivated by both increasing HBVDNA and ALT flare. Conclusion: HBV reactivation is a severe, life-threatening consequence of chemotherapy and immunotherapy in patients with chronic hepatitis B infection. Reactivation may be associated with DAA therapy in patients with HCV/HBV co-infection. HBV reactivation can be prevented through the use of pretreatment screening and anti-HBV prophylactic treatment