BACKGROUND: Excessive use of antibiotic growth promoters leaded in the creation of antibiotic-resistant bacteria and by consuming animal products, humans are at risk of receiving their residual. Therefore, instead of using antibiotics as growth promoters, some alternatives must be identified and introduced to animal breeders. Objectives: The purpose of this research was to study the effect of anise seed on performance, digestibility, and infectious microbes in the intestine of suckling calves. Methods: Twenty four female Holstein calves with average weight of39.8±3.8kg from the fourth day after birth to two weeks after weaning were examined in a completely randomized design to evaluate the effects of anise powder on dry matter intake, weight gain, age and weight of weaning, feed conversion ratio, apparent digestibility of dry matter, NDF and ADF, and intestinal infectious and harmful bacteria. The diets were: 1- Control, 2- 0.25% and 3- 0.5% anise/DM of diets. Results: Dry matter intake of calves did not affected by diets (p>0.05). At 70 days old the final weight of calves that consumed diets containing 0.25% and 0.5% of anise was significantly more than control diets. There was no significant difference between diets for the mean of total weight gain in whole period of experiment. The digestibility of NDF and ADF after weaning for diets contain anise was significantly more than control diet (p<0.05). Feed conversion ratio did not affected before weaning, but after weaning significantly improved compared with the control group for diet contain 0.25% and 0.5% anise (p<0.05). The age and weight of weaning were not affected by treatments. The Ammonia and pH of rumen fluid showed increase for anise diets compared with the control group (p>0.05). The adding of anise to the diets resulted in significantly decrease of E.coli of intestine of calves. Conclusions: Therefore, use of anise seed as a medicinal herb additive improved the performance of calves. Also, with the decline of E.coli population had beneficial effect on animal health and the environment. So it may be taking into account as good alternative for antibiotics.