Background: Breast cancer is the most common type of female malignancy. Increasing evidence in the last 10 years suggests that human cytomegalovirus (HCMV) is associated with several human malignancies including breast cancer. This study aimed to investigate HCMV in invasive ductal breast carcinoma by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry (IHC). Materials and Methods: A total of 50 samples of the cancer mass and non-neoplastic safe margin (SM) tissues of breast cancer collected then processed for paraffin block to apply IHC and hematoxylin-eosin staining. In addition to that, 30 blood samples collected from patients and healthy women (controls) for detection of anticytomegalovirus (antiCMV) IgG and IgM by ELISA. Results: About 38 samples (76%) of 50 samples diagnosed as invasive ductal carcinoma (IDC). The results showed that the presence of antiCMV antibody IgG in 100% of patients while the IgM presented in 76.7% of patients. There were significant differences (P < 0.05) between the optical densities of the IgG in breast cancer patients when compared healthy women. The positive results of CMV protein comprise 34 (89.4%) for immediate early 1 (IE1) protein, 35 (92.1%) for late protein, and 34 (89.4%) for phosphoprotein 65 (pp65) from 38 sample of IDC. The results also showed the absence of expression to CMV late and pp65 proteins and low percentage (10%) of IE1 protein in the SM tissues. Conclusion: Many studies including our observation indicated to the association of HCMV with breast cancer, but the role of HCMV in the pathogenesis of breast cancer is unclear.