The mean radiant temperature (T(mrt)) is the most important meteorological factor influencing human thermal comfort in urban areas. Numerous methods have been implemented for estimating T(mrt) using measured radiometer or thermometer data, and exhibit different levels of accuracy. This study presents a simple technique based on the traditional method (T(mrt_TM)) to estimate T(mrt) by utilizing measured radiation data from the radiometers. The estimated T(mrt) values from the six-directional method (T(mrt_SM)) and two black globe thermometer methods (T(mrt_BG) and T(mrt_BGv)) at two stations (sky view factor 0.69 and 0.94) in Jeju, Republic of Korea, for 8 days (5 sunny days, 3 (semi-) cloudy days) in spring and summer were used to validate the T(mrt_TM). The results showed that the mean differences between T(mrt_TM) and T(mrt_SM) were within the required accuracy for comfort in ISO 7726 (±?2 ?) on sunny days and were reduced to 0.1-0.3 ? in high T(mrt) conditions such as clear summer days. The T(mrt_BG) in most sunny and semi-cloudy days and T(mrt_BGv) on all days resulted in large mean differences from the T(mrt_TM) that exceeded the required accuracy for thermal stress in ISO 7726 (±?5 ?). Therefore, both black globe thermometer methods should be used carefully when estimating T(mrt), especially during sunny days. The correlations between T(mrt_TM) and T(mrt_SM) were highly significant, 0.93 on all days (p?=?0.01). The newly developed regression equations between T(mrt_TM) and T(mrt_SM) could reduce mean differences within 0.5 ? for all days, and their r(2) values exceeded 0.87. Therefore, the simple T(mrt_TM) technique can be used for T(mrt) estimation in human thermal comfort studies.