Existing masonry buildings represent one of the most vulnerable building typology if subjected to seismic actions. In the Groningen region a greater part of the building stock is represented by URM masonry buildings, where these structures were generally designed for gravity loads only. As a consequence of the induced seismicity in the study area, the strengthening of this class of structures is key factor. In particular, these URM buildings are characterized by poor masonry quality and not effective connections between vertical and horizontal elements, thus their strength cannot be activated to resist the seismic action as a whole system, preventing out-of-plane mechanisms and local collapses. This research concerns analytical analysis about in-plane capacity of masonry walls strengthened through an innovative technique employing fibres grids embedded in cementitious matrix layers applied on the wall’s surface. Externally bonded reinforcement with Fibre Reinforced Cementitious Matrix (FRCM) are system now widely used to repair and strengthen the existing structures. A Finite Element Model of unreinforced and reinforced walls has been developed and parameters defining masonry and strengthening materials have been verified by means of comparisons with the analytical results. The effectiveness of the FRCM strengthening system has been numerically and analytically investigated through a wide parametric analysis varying the wall slenderness ratio, the overburden load, the FRCM configuration, the masonry material properties and the FRCM material properties. The results evidence that, debonding is the governing failure mechanism for strengthened masonry piers before collapse occurs. They also confirm that for the specific cases study, the FRCM strengthening system added substantial increase to the in-plane capacity and deformation capacity of the masonry pier, showing thus the effectiveness of the FRCM as external reinforcements for masonry structures. Finally, suggestions for further research and improvements are also reported.