The present investigation was carried out to evaluate the effects of environmental factors on reproductive performance of bovine (Bos taurus) during summer, winter and spring for one year. The study was performed on free moving animals under natural condition during the two consecutive estrus periods by visual observation. The duration of estrus, numbers of mounts were observed. There was a seasonal effect on the duration of estrus; estrus was longer (P<0.001) in summer as compared to those of winter and spring. In addition, cows were mounted more times in estrus during winter than in summer and spring. The results of this study revealed that season influences on estrus behaviour of cows.