The aim of the study was to determine the effect of changes in body condition score (BSC) on milk yield and reproduction traits in early (30, 60 and 90 d, mid (120 and 150 d) and late lactation (210 and 270 d) in Holstein cows raised on a private dairy cattle farm in Kırşehir, Turkey. The data were obtained from 140 cows calved from November 2014 to November 2015. BSC groups were categorized as low, moderate and high in early lactation (<2.75, 2.75–3.00 and >3.00), mid- lactation (<3.00, 3.00–3.25 and >3.25) and late lactation (<3.25, 3.25–3.50 and >3.50). Cows with low and moderate BCS in early (BCS<2.75 and BCS=2.75-3.00), mid (BCS<3.00 and BCS=3.00–3.25) and late lactation (BCS<3.25 and BCS>3.50) had a higher aily milk yield (DMY), lactation milk yield (LMY) and 305-day milk yield (305-dMY) (P<0.05). Reproduction traits were also affected (P<0.05) by BCS in mid-lactation. In mid-lactation, the cows with low and moderate BCS had a shorter period of calving to the first service interval (CFSI) and lower number of services per conception (NSC) than that of the cows with high BCS (P<0.05). Both milk yield and reproduction traits were adversely affected by high BCS. It is suggested that BCS can be used as a reliable indicator in indirect selection programs for higher milk yield and reproductive performance in Holstein cows.