This paper reports the numerical results of the flexural response of ultra-high-performance concrete (UHPC) beams reinforced longitudinally with glass fiber-reinforced polymer bars (GFRP). In this paper, the finite element commercial software ABAQUS is used to evaluate the behavior of UHPC beams reinforced with GFRP bars through modelling a three-dimensional model subjected to four-point bending. Material and geometric nonlinearities were incorporated in the model to provide a valuable simulation that yields similar results to beam tested in the laboratory. For validation purposes, the finite element model is verified against existing experimental results that were conducted previously by the same authors. The main objective of this paper is to extend the numerical analysis to cover a more exhaustive set of parameters, including the effect of longitudinal reinforcement ratio and the beam’s cross-sections on the flexural capacity of the GFRP-UHPC beam. The results of the study revealed a significant improvement in the flexural capacity of UHPC beams with the increase in GFRP reinforcement. The load capacity of GFRP UHPC Beam was doubled when the GFRP longitudinal reinforcement ratio increased from 0.26 to 1.66%.