The effect on performance of adding calcium (Ca)-butyrate and Oleobiotec (a flavouring agent) additives to dairy calf starter diet was investigated. Thirty-two newborn Holstein calves (16 males and 16 females) were used in a completely randomized design with four treatments as: (1) diet with no additives, (2) diet containing Ca-butyrate, (3) diet containing Oleobiotec and (4) diet containing Ca-butyrate plus Oleobiotec. Milk of calves was supplemented with additives in the first 20 days of the study and then additives were top-dressed into the starter. Calcium-butyrate had no effect on starter and alfalfa intake during pre-weaning, post-weaning and over the whole trial period but it significantly increased the average daily gain and feed efficiency of calves during post-weaning and the whole trial period. Adding Oleobiotec did not change calf performance significantly. Furthermore, no synergistic effect of experimental additives on calf performance was observed.