Chlorine is the most frequently used disinfectant in water and wastewater treatment plants all over the world wide. This study investigated the effect of chlorine on phiX174 bacteriophages in treated sewage and drinking water samples which were inoculated separately with phiX174 either with or without autoclaving process. Then the samples were treated with different doses of chlorine solution for 15 and 30 min. Our results showed that the phiX174 bacteriophage was more efficiently reduced in the autoclaved samples than in the non-autoclaved samples. In the non-autoclaved treated sewage samples, treatment with 7 mg/l a of chlorine for 30 min was sufficient to remove 0.3 ± 0.07 log_10, while treatment with 12 mg/l of chlorine for 15 min efficiently remove 0.27 ± 0.05 log₁₀ of the initial phiX174 doses. Furthermore, we observed higher viral reduction in the autoclaved treated sewage samples after treatment with 11 mg/l of chlorine for 15 min which removed 1 ± 0.1 log₁₀ of the phiX174 initial dose. However, when non-autoclaved and autoclaved drinking water samples were treated with 3 mg/l chlorine for 15 min, it efficiently removed 1.2 ± 0.07 log₁₀ and1.4 ± 0.17 log₁₀ of phiX174, respectively. This reduction increased to 1.4 ± 0.08 log₁₀ and 2.3 ± 0.21 log_10, respectively, from the initial phiX174 dose when the contact time was increased to 30 min. However, phiX174 bacteriophage virus showed high resistance to different doses of chlorine in drinking water and treated sewage water samples.