Based on measurements of eye temperature (ET) (using infrared thermography) and rectal temperature (RT) (digital thermometer) in 83 clinically healthy dairy cows, an analysis of the relationship between these parameters depending on air temperature (Ta) was performed. A change in body temperature is recognized as an important indicator of illness or stress. The eye temperature is considered by experts from human and veterinary medicine to be the only truly relevant data and it can be characterized as a reliable indicator of body temperature and its changes. The measurements were carried out in the field conditions of a dairy farm, at average Ta of 5, 12, 19 and 25 °C.