This study presents the numerical modeling of size effect in shear strength of FRP-reinforced concrete (RC) beams with and without stirrups by finite element analysis (FEA) model. The size effect was incorporated in the model by controlling the mesh size, softening tensile stress-strain response, and dilation angle. A new modification was suggested to represent the softening tensile strength of concrete for different size of beams. The calibrated FEA model for beams with and without stirrups showed great power and ability in simulating the experimental results in terms of ultimate shear capacity, ultimate deflection, flexural and stirrup strains, and crack patterns. Additionally, the calibrated model was then verified by thirteen experimental results from four different studies, as well as a parametric study was performed.