Breast cancer is the leading type of malignancy and the leading cause of cancer-related deaths in women worldwide. The screening programs and advances in the treatment of patients with breast cancer have led to an increase in overall survival. Cancer registry systems play an important role in providing basic data for research and the monitoring of the cancer status. In this study, the results of the 10-year national cancer registry (NCR) of Iran in breast cancer are reviewed. NCR database records were searched for primary breast cancer records according to ICD-O-3 coding and the cases were reviewed. A total of 52,068 cases were found with the coding of primary breast cancer. Females constituted 97.1% of the cases. Breast cancer was the leading type of cancer in Iranian females, accounting for 24.6% of all cancers. The mean age of the women with breast cancer was 49.6 years (95%CI 49.5-49.6). Most of the cases (95.7%) were registered as having invasive pathologies (behavior code 3). The most common morphology of primary breast cancer was invasive ductal carcinoma (ICD-O 8500/3) followed by invasive lobular carcinoma (ICD-O 8520/3) with relative frequencies of 77.8% and 5.2%, respectively. The average annual crude incidence of primary breast cancer in females was 22.6 (95%CI 22.1-23.1) per 100,000 females, with an age-standardized rate (ASR) of 27.4 (95%CI 22.5-35.9). There were no data on survival, staging or immunohistochemical marker(s) of the breast-cancer-registered cases. The incidence of breast cancer in Iran is lower than in low-middle-income neighboring countries. The NCR data registry of breast cancer is not accurate in monitoring the effect of screening programs or determining the current status of breast cancer in Iran. Screening programs of breast cancer in Iran have failed to enhance the detection of the patients with in situ lesion detection. A quality breast cancer registry and a screening program for breast cancer are both needed.