The main focus of this project is the development and characterization of natural fiber reinforced composite materials that are suitable for structural applications utilizing geopolymer matrices. This study presents the mechanical and fracture behavior of geopolymer composites reinforced with flax fibers and also shows how to affect the mechanical properties of the geopolymer composite by varying sodium hydroxide concentration. The geopolymer has been synthesized from low calcium fly ash, sodium silicate and sodium hydroxide solution. Flax fibers (0.6wt%, 0.8wt%, 1.2wt% & 2wt %) were distributed unidirectionally and randomly within the geopolymer matrix. The compressive strength analysis showed the appropriate content of fiber and sodium hydroxide concentration lead to improved compressive strength of the geopolymer composite compared to the pure geopolymer matrix. The failure mechanism of the composite was shown to be different, unlike pure geopolymer that displays ceramic like brittle failure. Scanning electron microscopy (SEM) analysis was used to evaluate the fiber/ matrix interface and fracture surfaces indicated that fiber pullout is the possible toughening mechanism. The quality of the interface between the fiber and the matrix was characterized based on the imprint of the fibers on the matrix. The new environmentally friendly composites have potential applications in the construction and other specialized sectors.