Geopolymers are representing the most promising green and eco-friendly alternative to ordinary Portland cement and cementitious materials, thanks to their proven durability, mechanical and thermal properties. However, despite these features, the poor tensile and bending strengths usually exhibited by geopolymers due to their brittle and ceramic-like nature, can easily lead to catastrophic failure and represent the main drawback limiting the use of those materials in several applications. Fiber reinforced geopolymer composites may be considered a solution to improve flexural strength and fracture toughness. Different types of dispersed short fibers are here investigated as a reinforcing fraction for a geopolymer matrix based on an alkali-activated ladle-slag. It has been demonstrated that both organic and inorganic fibers can lead to a significant flexural strength enhancement. Moreover, the investigated geopolymers exhibit an increase in toughness, thus determining a switch from a brittle failure mode to a more ductile one