<p>32 °C is defined as the initial high-temperature condition. While the adverse effects of this temperature alone on the human body are relatively limited, the addition of thermal radiation may lead to significant negative impacts. However, there is a notable lack of relevant research specifically addressing this temperature condition. This study conducted climate chamber simulation experiments with three designed conditions: 26 °C, 32 °C, and 32 °C with an additional 2 kW/m² thermal radiation source. During the experiments, subjects remained seated 1.5 meters from the radiation source, resulting in a measured irradiance of 195 W/m² on the frontal body surface. Over a 135-minute exposure period, physiological parameters and subjective sensations were evaluated for 36 subjects, and cognitive performance was assessed using ten different tests. Compared to the 26 °C condition, exposure to 32 °C alone had a limited impact on physiological parameters, subjective sensation, and cognitive performance. However, with an added 2 kW/m² thermal radiation source at 32 °C, the core temperature, skin temperature, heart rate, the low-frequency to high-frequency ratio (LF/HF), and weight loss increased significantly. Thermal discomfort and thermal unacceptability also rose markedly, and acute symptoms related to neurobehavioral function intensified. Notably, performance declined significantly in a greater number of cognitive tests, including the stroop test, Tsai-Partington (TP) test, 1-back test, and both high/low load tests. These results indicated that the addition of thermal radiation at 32 °C elevated occupational safety risks. This study provides a theoretical basis for establishing new safety standards for work conducted under combined high-temperature and thermal radiation conditions.</p>