In order to evaluate the effect of essential oil of mixed herbs in starter feed, with and without alfalfa and under mild heat stress, on growth performance and health parameters in Holstein dairy calves, 40 calves, male and female (ratio of 7 to 3 per each treatment, respectively) with mean body weight of 42 ± 0.4 kg were used in the experimentDietary treatments were: a) starter, b) starter + 10% forage, c) starter + 0.2% bioherbal, and d) starter +10% forage + 0.2% bioherbal. This mixture named animal bioherbal, which was supplemented by essential oils of Coriander , Cumin , Peppermint and Lemon grass . Calves were weaned at 50 days of age and to 20 days after the weaning were present in the experiment. Feed intake were measured weekly, weight gain was done once every two weeks, fecal score was record daily and fecal samples for parasite identification were collected in days 7, 8, 35 and 70 of age. The results of this study show that dry matter intake (DMI) was influenced by treatments at pre weaning and post weaning (P 0.05), and DMI for calves used starter + alfalfa was highest numerically. Bioherbal consumption numerically reduced DMI in treatment with and without alfalfa at pre and post weaning and in the whole trail. Average daily gain (ADG) was influenced by treatments at pre weaning and post weaning (P 0.05) and in the whole trail (P=0.05), and ADG for calves used starter + forage were highest and did not have significant difference with treatment of starter + forage + bioherbal. Feed efficiency tended to be significant at pre weaning (P=0.093) but at post weaning (P=0.790) and whole trail (P=0.185) was not significant. For any of the performance parameters, effect of treatment × period was not significant. The effect of treatment on digestibility of dry matter and organic matter tended to be significant (P=0.08) but for protein, NDF and ADF was not significant by treatment. Bioherbal consumption in treatment with and without forage caused an improvement in digestibility of nutrients. Body measurements and behaviors were not influenced by treatments. Fecal score before weaning was not affected by treatment but after that was influenced (P 0.05), and presence of bioherbal caused an increase in fecal score. Rumen fluid pH for post weaning was affected by treatment (P 0.05) and treatments had no effect on VFA and rumen Ammonia_N concentration. In conclusion, the result indicated that using bioherbal has no significant effect on performance and did not have any effect on the health parameters. Keywords: Essential oil mixed, Herbs, Animal bioherbal, Mild heat stress