Background: Cancer breast (BC) is the commonest worldwide malignancy in females. KI-67 one of prognostic biomarker in breast cancer. Objective: Assessing KI-67% expression in relationship with disease free survival (DFS), over-all survival (OS) and various clinic-pathological parameters of the disease (age, menopausal status, tumor size, nodal status, histological type/ grade, Estrogen receptors Progesterone receptors (ER, PR) status and Human Epidermal Growth Factor Receptor (HER2neu) status. Patients and Methods: This study included 115 female breast cancer patients were done KI-67% biomarker. Our cases at Clinical Oncology Department, Al-Hussein University Hospital during the period between January 2014 and December 2017. Results: Cutoff value of KI-67% was significance (P-value < 0.01) with (ER, PR and HER2neu), significance (P-value < 0.05) with DFS and insignificance (P-value > 0.05) with OS, age, menopausal status, tumor size, nodal status, histological type/ grade). Conclusion: Patients with high KI-67% showed significantly poorer prognosis than those with low KI-67%. This may show that KI-67% was the most robust independent prognostic factor in multivariate prognostic analysis, despite having very strong correlations with other biomarkers such as hormone receptor status (ER & PR) and HER2neu. KI-67% might be helpful in identifying patients who have a favorable diagnosis and in preventing unnecessary treatment for these women.