The present investigation aimed to study the effects of season of calving on the ovarian activity of crossbred cows. A total number of 10 crossbred cows was used in this study. The cows were divided into two groups the first group (5= cows) calved during the cold season and the second group (5= cows) calved during the hot season. The results demonstrated that the uterine involution in that cows calved during the cold season was lower (30.80±0.80, days) than hot season (32.40±0.25, days) (P<0.05). The post-partum service interval and number of services per conception of cows was (35.20±5.52 and 35.60±5.55 days) and (1±0.0 and 1.2±0.2, services) in cold and hot season respectively. The interval from calving to the conception was lower in the cold season (35.20±5.52, days) than hot season (40.40±8.46 days) (P<0.05). Conception rate from the first service was significantly (P<0.05) higher (100%) in the cold season compared to hot one (80%). There was no significant (P<0.05) difference of gestation period (GP) between two groups was 284.20± 1.2 and 284.0± 1.5 days in in cold and hot season respectively. However, the calving interval in cows was significantly (P<0.05) lower (319.40±1.35, days) in the cold season group compared to the hot season (342.40± 1.55 days). This study proved that the reproductive performance of crossbred cows in Aswan Governorate during the cold season was better compared to the hot season. Therefore, cow breeders in Aswan Governorate recommend the necessity of arranging the birth of cows during the cold months.