At present, soil and mineral based building material such as bricks are one of the main components in building construction in Malaysia. This building material is a direct source of radiation exposure since it contains naturally occurring radioactive materials (NORM). In this study, clay brick samples used were obtained from 7 factories in Selangor and Johore, Malaysia. The activity concentrations of 226 Ra, 232 Th and 40 K in these samples of clay bricks were determined using a comparative method and was analysed using gamma spectrometry with HPGe detector. The mean values of activity concentrations for 226 Ra, 232 Th and 40 K were found to be in the range of 39.04 ± 0.88 Bqkg-1 - 73.61 ± 5.32 Bqkg-1, 43.38 ± 2.60 Bqkg-1 - 73.45 ± 1.51 Bqkg-1, and 381.54 ± 11.39 Bqkg-1 - 699.63 ± 15.82 Bqkg-1, respectively. The radiation hazard of NORM in the samples was estimated by calculating the radium equivalent activity (Raeq), external hazard index (Hex) and internal hazard index (Hin). Radium equivalent activity (Raeq) determined was in the range of 151.90 Bqkg-1 - 194.22 Bqkg-1 which is lower than the limit of 370 Bqkg-1 (equivalent to 1.5 mSvyr-1 ) recommended in the NEA-OECD report in 1979, whereas external hazard index (Hex) and internal hazard index (Hin) were between 0.20 – 0.26 and 0.52 - 0.71 respectively. The annual effective dose rate exposure to a dweller received from the clay bricks was calculated to be in the range of 0.35 ± 0.18 mSvy-1 - 0.43 ± 0.09 mSvy-1.