In the current research, water samples were collected from selected sites in the Tigris River. The water samples were collected monthly started from September 2017 to January 2018.The results demonstrate that the total average values of radon activity level for the 5 months for site 1, site 2, site 3 and site 4 were 36.6, 28.5, 46.2 and 37.2 Bq.m−3, respectively. The average radon concentration value of the four sites during the 5 months was 37.1 Bq.m−3. Dissolved radon concentrations for the study samples were also calculated and their average values were 1.242, 0.930, 1.510 and 0.930 Bq.L−1 for site 1, site 2, site 3 and site 4, respectively. The overall average calculated radon surface exhalation rate for the water samples was 0.363 Bq.m−2.h−1. Annual effective doses due to water consumption for adults, children and babies were also calculated. The obtained values of radon concentrations in the study water samples were found to be lower than the maximum permissible concentrations in water as recommended by the US Environmental Protection Agency (EPA). Also, the results reveal that the radon activity level has its lowest value during November but that there are no considerable variations with different times of the year.