The first outbreak of lumpy skin disease (LSD) occurred in South Korea in October 2023, and cattle are being vaccinated countrywide to prevent its spread. However, studies regarding the changes in body temperature and activity after LSD vaccination during pregnancy are lacking. Therefore, this study aimed to compare the ruminoreticular temperature and body activity of 18 pregnant and 28 non-pregnant cows using a bolus sensor after LSD vaccination. Two days after LSD vaccination, the ruminoreticular temperature of all the experimental groups increased and that of the pregnant cows remained very high 3 to 5 days after vaccination compared with that in the non-pregnant cows. The rate of maintaining ≥ 40°C was 12.8% in non-pregnant cows and up to 20.8% in pregnant cows. Body activity also temporarily increased in pregnant cows compared with that in the non-pregnant cows on the 1st and 4th days after vaccination. The results of this study may be applied to prevent the rise in ruminoreticular temperature and used as raw data by veterinarians when LSD vaccine is administered during pregnancy.