Background: Brucellosis as a zoonotic disease is widespread among human and animal that it continues to be a major public health problem. Due to the shortage of recent epidemiologic data regarding the brucellosis distribution in Iran, we convinced to evaluate the prevalence of brucellosis in provinces of Iran. Methods: In this descriptive study, data were collected from brucellosis suspected patients referred to Noor Pathobiology Laboratory, Tehran, Iran from 18 out of 31 provinces of Iran during 2013-2015. Results: Overall, 2635 out of 17103 attending cases (15.4%) were recognized as brucellosis patients. The most prevalent rate was found in patients aged 20-39 yr old (41%) which of them 67% were male. Patients with brucellosis were significantly diagnosed in spring season (Apr to late May). Among included provinces, Hamadan Province had the highest (25%) prevalence followed by Markazi and Mazandaran with 24.7% and 22.5%, respectively. Conclusion: Brucellosis is still considered as an important infectious disease with a high prevalence in many provinces of Iran. It is necessary to implement a national brucellosis control program by increasing medical education, public knowledge and various controlling plans for preventing, controlling and eradicating of brucellosis.