Portland cement is considered as an important basic material used for building construction. One of the main concern is that people spend more than 80% of their time indoors and they are eventually exposed to the cement or its raw materials for a long time. Therefore, assessment of natural radioactivity levels and radiological hazards associated with these materials is necessary. In this study, a total of 25 samples of five Portland cement brands favorably used in Thailand were analyzed by using gamma-ray spectrometry technique. The observed specific activities of 226Ra, 232Th and 40K together with the radium equivalent activities were compared with the reported data for other countries and the world recommended levels proposed by the UNSCEAR–all obtained values were found within the acceptable limits. Additionally, for evaluation of radiological risk, six hazard parameters were considered. The estimated values of absorbed dose rate, external and internal hazard indexes, gamma and alpha indexes, annual effective dose equivalent, and excess lifetime cancer risk, all of them were found below the international standard of the maximum acceptable limits. Therefore, these studied results primarily confirm that all five brands of Thai Portland cement type I are radiologically safe to be used as construction materials with no significant impact of radiological hazards provided.