Concrete is a widely utilized material in the construction industry with cement as the binder components. The production of cement contributes to one ton of emitted CO2 per ton of produced cement. Therefore, there was a need to find a suitable alternative binder using available resources and chemical reactions, such as the geopolymer concrete. This study investigates the flexural behavior of geopolymer concrete slabs reinforced with different types of reinforcement rebars, forming a successful step toward sustainability and green construction principles. The superior properties of the fiber-reinforced polymers (FRP) were also included using various types of reinforcements, such as carbon (CFRP) and basalt (BFRP) where their high tensile strength contributes to the slab’s flexural performance. Slabs with different geopolymer concrete strengths (20, 40, and 60) MPa and different internal reinforcement rebars (steel, CFRP, and BFRP) were simulated using ABAQUS software. Results revealed that the presence of geopolymer concrete with higher strength increased the induced cracking severity and reduced the slab’s ductility. In addition, the strength was significantly upgraded using FRP reinforcement with the optimal combination with lower geopolymer concrete grades.