Objectives: The aim of this study was to determine the physiological and biochemical changes among bakers, induced by heat exposure at the workplace. Material and Methods: Information was collected by means of a self-administered questionnaire. Vital signs were measured and recorded by a trained nurse before and after each work shift. A venous blood sample was drawn at the end of each work shift. The mean wet-bulb globe temperature (WBGT) index in the bakeries and offices was measured. Results: This was a cross-sectional study involving 137 bakers working in 20 bakeries, and 107 control subjects comparable in terms of age, race, marital status, years of service, income, and cigarette smoking. There was a significant weight loss and increase in the respiratory rate, the heart rate, and oral body temperature among the bakers compared to the control group. Sodium levels were significantly lower, while blood urea nitrogen levels were significantly higher, among the bakers than in the control group. There were unfavorably hot working conditions in the bakeries: the WBGT index in the bakeries was 37.4°C while the average WBGT for the offices was 25.5°C. Conclusions: The changes in the physiological and biochemical parameters among the bakers were found to be associated with exposure to high environmental heat in the bakeries, as judged by the WBGT index. Preventive measures should be aimed at reducing the adverse effects of heat exposure among bakers and should be directed towards the man-machine-environment triad. Int J Occup Med Environ Health. 2022;35(3):265–72