Retrofitting existing concrete buildings is vital. Using Fiber-Reinforced Polymer (FRP) composites, especially Carbon FRP (CFRP), significantly improves structural performance. The eXtended Finite Element Method (XFEM) is a superior modeling tool for such retrofitted structures, offering precision. This study uses XFEM in Abaqus to parametrically analyze CFRP-retrofitted concrete beams under flexure. Key examined parameters are concrete compressive strength (20-60 MPa), CFRP sheet thickness (0.1-0.2 mm), and the notch-to-beam height ratio (0.2-0.4). Results show that beams with lower concrete strength (20 MPa) exhibit 59% lower load capacity compared to higher strength concrete (60 MPa). Increasing CFRP thickness from 0.1 mm to 0.2 mm increases ultimate load by 68% and ductility index by 55%. While the first maximum load is minimally affected by CFRP thickness and depends on the concrete, the ultimate load increases sharply with thicker CFRP, indicating that the ultimate load is critically linked to CFRP activation after concrete cracking. Furthermore, increasing notch height from 40 mm to 60 mm reduces the first maximum load by 34% but affects the ultimate load by only 9%. In conclusion, CFRP retrofitting effectiveness is highly influenced by material and geometric properties, with XFEM providing accurate behavioral predictions for optimized strengthening designs.