Background: Breast cancer is the most common cancer in Iraq and the United Kingdom. While the disease is frequently diagnosed among middleaged Iraqi women at advanced stages accounting for the second cause of cancer-related deaths, breast cancer often affects elderly British women yielding the highest survival of all registered malignancies in the UK. Objective: To compare the clinical and pathological profiles of breast cancer among Iraqi and British women; correlating age at diagnosis with the tumor characteristics, receptor-defined biomarkers and phenotype patterns. Methods: This comparative retrospective study included the clinical and pathological characteristics of (1,940) consecutive female patients who were diagnosed with invasive breast cancer from 2014 to 2016 in Iraq (Medical City Teaching Hospital, Baghdad: 635 cases) and UK (John Radcliffe, Oxford and Queen's, BHR University Hospitals: 1,305 cases). The studied parameters in both groups comprised the age of the patient at the time of diagnosis, breast cancer histologic type, grade, tumor size, lymph node status, clinical stage at presentation, Estrogen Receptor (ER), Progesterone Receptor (PR) and HER2 positive tumor contents and the receptor defined breast cancer surrogate subtypes. Results: The Iraqi patients were significantly younger than their British counterparts and exhibited higher trend to present at advanced stages; reflected by larger size tumors and frequent lymph node involvement compared to the British (p<0.00001). They also had worse receptor-defined breast cancer subtypes manifested by higher rates of hormone receptor (ER/PR) negative, HER2 positive tumor contents, Triple Positive and Triple Negative phenotypes (p<0.00001). Excluding HER2 status, the significant differences in the clinical and tumor characteristics between the two populations persisted after adjusting for age among patients younger than 50 years. Conclusion: The remarkable differences in the clinical and tumor characteristics of breast cancer between the Iraqi and British patients suggest heterogeneity in the underlying biology of the tumor which is exacerbated in Iraq by the dilemma of delayed diagnosis. The significant ethnic disparities in breast cancer profiles recommend the prompt strengthening of the national cancer control plan in Iraq as a principal approach to the management of the disease.