Fabric-Reinforced Cementitious Matrix (FRCM) composites are materials used for strengthening of reinforced concrete structures, serving as an alternative to FRP (Fiber-Reinforced Polymers) composites. They are often utilized in cases where the use of FRP composite strengthening is problematic or impossible, due to factors such as fire safety requirements or the conservation needs of historic structures. Because of their lower efficiency compared to FRP composites, they are the subject of research aimed at improving their effectiveness. The article presents the influence of PBO-FRCM (PBO – p-Phenylene BenzobisOxazole) composite mesh anchorage on the load bearing capacity and deformability of strengthened reinforced concrete slab elements. The analysis is based on the results of an experiment in which seven reinforced concrete elements were tested under bending. Six of these elements were strengthened in flexure using FRCM composites with different types of PBO mesh anchorage. The study analyzed the deformations of both the base reinforced concrete elements and the strengthening composite. The conducted research showed that in slab elements, the anchorage of the composite mesh marginally improves the load-bearing capacity of the elements, but it allows for the improvement of selected deformation parameters of the elements. The composite failure mechanism involving the tearing of high-strength composite fibers has not been observed, which indicates an incomplete utilization of the material’s potential and suggests further developmental possibilities in this area.