Breast cancer is the most common cancer among women, and in 2002 it was expected that 636,000 new cases would occur in developed countries and 514,000 in developing countries. Although the incidence rate of this cancer in Asian countries is lower than in Western countries, whereas the incidence trend increasing rapidly in Asia. Using the data from the Cancer Registry System, this study was carried out to investigate the incidence trend during 2000–2005 in Iran and its six geographical areas. The incidence rates were standardized according to age-sex groups by Excel directly and confidence intervals is calculated for the point estimations by Stata11. The trends were analyzed separately based on gender, age groups for different provinces by Poisson regression in Stata11. The age standardized incidence rate in 2000 was 0.1 and 3.4 per 100,000 in males and females, respectively, reaching 0.5 and 16.7 per 100,000 in 2005. The incidence trends in all geographical areas of the country were increased despite the difference in the slopes. The sex ratio of male to female was 31.6 and the mean age of the patients was 49.4 (±12.6) years. The incidence of breast cancer in Iran was lower than the European and Asian countries but the trend is in rising. Although this increase is due to the increase in the prevalence of risk factors among Iranian population. Improvement in the coverage of the cancer registry system as well as the screening programs are important factors for these changes.