Farmed cervids are not fully domesticated animals, usually kept on large open pastures. However, in intensive breeding farms, animals are often kept indoors during the winter in order to obtain desirable weight gain or avoid deaths. The aim of the study was to assess the stress level in farmed fallow deer (Dama dama) kept indoors during the winter with a changed photoperiod, as well as to analyze the effect of the cortisol level on the animals depending on their age and body mass. Two groups of adult fallow deer males, 15 individuals each, with an average age of 5.9 years, were used in the study. The experimental group was kept in a utility room with a changed photoperiod and a temporary access to an enclosure, while the control group spent the entire time in an outdoor enclosure. Blood samples were collected from all animals three times, at monthly intervals, to determine the cortisol concentration. No differences were found between the study groups. The average cortisol level ranged from 2.86 to 3.92 μg/100 ml in the experimental group and from 3.13 to 3.46 μg/100 ml in the control group. The average cortisol concentration in older stags was similar to that in younger males (3.48 μg/100 ml and 3.42 μg/100 ml, respectively). Simple manipulation procedures do not affect the welfare of farmed fallow deer. Cervids tolerate natural winter conditions well both on the run and in utility rooms with appropriate space.