Breast cancer is the most common non-skin malignancy and the second leading cause of death due to cancer in women (after lung cancer). Several factors involved in this disease have been studied. EBV has been proposed as a possible cause of breast cancer in humans. Information related to the possible association of EBV with breast cancer is contradictory and inconclusive. Therefore, we started to examine the role of this virus in breast cancer. The study was conducted on paraffin-embedded samples of patients with breast cancer (case or experimental group) and fibrocystic lesions (control group) available in the archives of pathology laboratory of Shahid Beheshti Hospital of Kashan related to 2012-2013. Samples DNA was extracted and infection with EBV virus was analyzed using PCR method. SPSS-21 was used for data analysis. The frequencies were compared with Chisquare test and the means with t-test. In this study, out of 40 patients with cancer, 14 patients (35%), and out of 40 patients with fibrocystic lesion, 25 patients (62.5 percent) were positive regarding EBV virus (p=0.02). In the samples of cancer, no significant differences were obtained between the two groups of positive and negative EBV in terms of average age (p=0.38), average menarche age (p=0.16), average age of menopause (p=0.18), and the average age the first birth (p=0.97). In addition, no statistically significant differences were observed between positive and negative groups in terms of tumor size. The results of this study showed that EBV is significantly more in fibrocystic lesions than in breast cancer. Thus, no etiologic relationship was found between EBV infection and Invasive Ductal Carcinoma (IDC) of Breast in this study, and more research is needed to clarify the role of this virus in causing breast cancer.