Abstract: Effects of 6 different calving intervals on the milk yield traits of Holstein–Friesian cattle were investigated. The intervals were 325 days and below (1), 326-345 (2), 346-375 (3), 376-400 (4), 401-450 (5) and 450 days and above (6). Maximum 305- day milk yield, average daily milk yield and actual milk yield were obtained on the 6th group and the longest lactation length was obtained on 4th calving interval group. Averages of the 305-day milk yield, actual milk yield and average daily milk yield obtained from 2nd group was higher than 3rd, 4th and 5th calving interval groups. The effect of the groups on 305 - day milk yield, actual milk yield, average daily milk yield and lactation length was found statistically insignificant. The correlation coefficient between calving interval and 305-days milk yield was 0.18. R2 originated from calving interval was 3.2% for 305-day milk yield. In conclusion, these result, indicated that the 326–345 days length on calving intervals did not have any negative effect on milk production traits of Holstein Friesian cattle.