Background: The HER-2/neu gene is altered in 15-20% of breast cancer patients. Immunohistochemistry (IHC) is considered to be the most cost-effective method for HER-2 detection in many countries. Approximately 8,000 new cases of breast cancer are observed annually in Iran. The aims of this study were to conduct a systematic review of the literature on the rate of HER-2-positive breast cancer diagnosed by IHC in Iran. Methods: A systematic search of the medical literature using the Medline/PubMed, ISI and SID databases revealed articles published in the English and Persian languages evaluating HER-2-positive breast cancer in Iran. Results: From 22 studies, 3,033 patients were evaluated, of whom 1,350 were diagnosed as HER-2-positive by IHC HER-2 testing. The mean percentage of HER-2-positive patients was 44.5%, which is higher than that recorded in international statistics. Results of this meta-analysis showed a significant heterogeneity between ratios. There was a statistically significant difference between the results of pre- and post implementation of 2007 American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) guideline. IHC HER-2 testing has been performed in Iran for over 10 years. Similar to many other countries, before establishment of an infrastructure for IHC diagnostic tests, HER-2 testing was routinely performed in Iran. Our study showed that the statistics reported from Iran varied widely; for instance, the rate of HER-2-positive cases varied from 23.3% to 81.0%. Conclusions: Our results demonstrate that the lack of standardization and harmonization of this test have led to marked variations in breast cancer diagnosis in Iran.