Introduction - One of the most important hormones affecting reproductive and milk yield is insulin-like growth factor I (IGF-I). IGF-I is closely related to nutritional status and the post-partum ovarian activity in dairy cows. It also stimulates milk synthesis and its secretion. Body condition score (BCS) is a useful management tool routinely used to predict body fat storage and energy status in dairy cows and has a strong influence on milk production and reproductive efficiency for the upcoming lactation after calving. Many publications have been available on BCS and serum or plasma IGF-I in Holstein cows. However, the information regarding the milk of Jersey cows has been limited. Therefore, further studies have been required to reveal the effect of IGF-I and BCS on reproduction and milk yield traits of this breed.