Chlorine disinfection of drinking water containing natural organic matter leads to the formation of brominated trihalomethanes (THMs) in the presence of bromide ions. In the present study, the results of an experimental investigation into the factors forming THMs in the presence of bromide ions are presented. The experiments were conducted using samples collected from Zai water treatment plant in Jordan under different operating conditions such as reaction time, temperature, pH, TOC, and the ratio between bromide ions and initial chlorine dose. The experimental results showed that the formation of all brominated THMs, mainly CHBr3), increased with increasing of any of these parameter values and decreased chloroform formation. CHCl2Br and CHClBr2 increased with increasing the experimental parameters and thereafter remained constant or slightly decreased. Moreover, n(Br) values which represents Bromine incorporation into THMs are almost in the range from 2.5 to 2.7. However, the values of n(Br) increased with increasing bromide concentration and remained constant or slightly decreased with increasing contact time under the studied range of bromide ion concentrations.