The aim of the present study was to evaluate the relationship between cognitive performance, health and environmental comfort as a function of indoor air temperature (T-a) variation. A total of 360 undergraduate students were subjected to the variation of the T-a at 20, 24 and 30 degrees C; their thermal responses were evaluated over three consecutive days. Performance variables measured in the study were cognitive performance, blood pressure, heart rate (HR) and comfort. The environmental variables measured were T-a, globe temperature (T-g), illumination, noise, airflow velocity and air quality. The variation in HR was influenced by the variables, relative air humidity and mean radiant temperature (T-rm) during the three days of observation, where HR was higher than 100 bpm when T-g was greater than T-a. T-rm increased proportionally to the increase in T-g, thus characterising heat exchange by radiation. The number of correct answers and test response time were also positively influenced by T-rm when T-a was 20 degrees C. Teaching environments (TEs) with increased heat load due to the individual body heat of students, increased outdoor T-a and urban morphology associated with the building of the TEs result in increasing in T-rm due to the T-g being higher than the air temperature, with possible impacts on health and performance variables.