Background : From 2008 to 2012 worldwide there are 124.8 new cases of breast cancer per 100,000 female population. One of the best prognostic factor in breast cancer is histological grade, which is an assessment of morphological characteristics of tumor and has been shown to provide important information related to the clinical behavior of breast cancer. The expression of HER-2 (human epidermal growth factor receptor-2) is a prognostic and predictive factor in patients with breast cancer. Knowledge of HER-2 expression in breast cancer patients can be used as a prognostic factor, and the development of specific targeted therapy for HER-2. This study was conducted to determine the comparison between grade histology and overexpression of HER-2 breast cancer patients. Objective : To determine the comparison between overexpression of HER-2 with histological grade in breast cancer patients. Methods : Cross-sectional study conducted on 84 patients with a diagnosis of breast cancer that has been conducted immunohistochemical examination (HER-2) and histopathologic (histological grade). Sample was taken from January to December 2015. Data analysis by Chi-Square test done gradually include univariate and bivariate analysis. Result : Of the 84 samples of research showed patients with histological grade I and II were 62 (73.81%) peoples, and histological grade III by 22 (26.19%) peoples. The expression of HER-2 positive in 32 (38.09%) peoples, and HER-2 negatif for 52 (61.91%) peoples. By using the Chi-square test of correlation values obtained P = 0.208 for the comparison between histological grade and overexpression of HER-2. Conclusion : There was no correlation between HER-2 overexpression with high histological grade (grade III) in breast cancer patients.