Background: Cyclin D1 can function as an oncogene that favours a proliferative advantage to tumor cells. Recent evidences strongly suggest the role of Cyclin D1 in breast cancer resistance to therapy and cancer progression. Objectives: To evaluate the immuno-expression of Cyclin D1 and correlate this with clinicopathological parameters, which are known to be prognostic factors, thus evaluating the role of cyclin D1 as a prognostic marker in breast carcinoma. Materials and methods: Fifty-two cases of invasive breast carcinoma removed by modified radical mastectomy were enrolled in this study and evaluated for expression of Cyclin D1 by immunohistochemistry. The expression was evaluated by the Allred score that combines the intensity of immunoreaction with the percentage of positive cells. Results: Cyclin D1 expression appeared as brownish nuclear staining and showed variation in its expression among different types of invasive breast carcinoma. It showed significant correlation with tumor grade (p= 0.004), histologic type (p= 0.014), luminal molecular subtype (A&B) tumors (p= 0.001), estrogen receptors (ER) (p= 0.02), progesterone receptors (PR) (p= 0.007), and tumors of cases were received Neoadjuvant chemotherapy (NCT) before surgery (p= 0.049). Conclusion: The current data suggests thatCyclin D1protein have a role in breast oncogenesis and is involved in progression of breast carcinoma as its expression is correlated with many prognostic factors. Therefore, it may serve as a prognostic marker for patient outcome and may help in making an appropriate strategy of adjuvant therapy selection.