Breast fibrosis (BF) is one of the most reported late toxicities following whole breast radiotherapy (WBRT). This study aims to find out biomarkers that can be used in individual risk assessment of BF. The correlation of surgical and dosimetric parameters with BF was also analyzed. Two hundred twenty-three invasive breast carcinoma patients who underwent breast conserving surgery and adjuvant WBRT +/-regional nodal irradiation were included in the study. Age, lumpectomy size, microscopic tumor size, systemic treatment status, the time from surgery to WBRT were the clinicopathological features evaluated. The volume of the whole breast and boost volume and their ratio, the maximum and mean dose of the breast, the dose of 95% of breast volume, the percent of the breast volume that had 50Gy and more (V50), V55, and V60 were the parameters evaluated. Neutrophil/lymphocyte, platelet/lymphocyte, lymphocyte/monocyte, systemic immune-inflammation index, hemoglobin, and C-reactive protein (CRP) levels before WBRT, the ratio of hemoglobin and CRP levels before and after WBRT were the biomarkers that investigated for prediction of BF. The median follow-up time was 22.5 (6-85.29) months. Grade 1 fibrosis was observed in 107 (47%), and grade 2 fibrosis in 7 (3.1%) patients. In the grade 1-2 fibrosis group lymphatics irradiation rate was higher (51.8% vs 35.8%, p= 0.016) and the treated breast in this group were mostly left-sided (left side percentages: 38.5% vs 56.1%; p= 0.008). CRP-Ratio was the only parameter that had statistically significant ROC curve (Area under the curve: 0.412, p= 0.024). The CRP-Ratio value of 0.544 was found to have the best sensitivity (35.65%) and specificity (84.25%).