Background: The expression level of HER2 gene is low in normal breast tissue, but levels of these receptors are higher in half of cases of breast cancer. Different expression levels of HER2 gene in normal and malignant cells have made this gene an ideal biomarker for therapeutic purposes. In this study, the extent of HER2 overexpression and its relationship with the age and the occurrence of metastasis were evaluated in breast cancer patients. Methods: In this cross-sectional study, 62 patients with breast cancer were evaluated at oncology clinics in Ilam province. Clinical examination for metastasis, examination of tissue samples for HER2 gene expression, and information related to variables were recorded in a breast cancer registry. The obtained data were analyzed using SPSS 20 statistical software by appropriate statistical tests.Results: The mean age of the participants was 48.37 ± 10.98, and 98.4% were women. The prevalence of increased HER2 gene expression was 37.1% in patients. There was an inverse relationship between patients' age and HER2 positivity (P value = 0.02). The chance of metastasis was 9 times higher (OR = 9.82) in cancer patients who had the HER2 gene expression Conclusion: In Ilam province, the prevalence of HER2 positivity in breast cancer patients is almost similar to other parts of the country and is associated with the occurrence of metastasis and low age of breast cancer patients.