This paper presents a study on the efficiency of Fiber Reinforced Polymer (FRP) composites in the shear strengthening of stone masonry walls, which are characteristic for architectural heritage buildings in Slovenia and elsewhere. Developing preservation and strengthening strategies to ensure the structural integrity and resilience of masonry under seismic conditions is very important and modern approaches include shear strengthening of masonry with FRP composites. This paper utilizes analytical/empirical models to estimate the contribution of FRPs to masonry walls’ shear resistance in various code provisions and literature. A short overview of the standards is provided, summarizing which specific strengthening methods, configurations and other parameters models consider. The studied analytical models were compared to results of two selected experimental studies conducted in Slovenia. In both studies, unstrengthened stone masonry walls were tested first, followed by application of retrofitting and strengthening measures and further in-plane cyclic lateral testing to assess the applied strengthening system’s contribution. The effectiveness of FRP systems in enhancing shear capacity of stone masonry walls is presented for both considered experimental campaigns. Finally, the conducted comparative analysis between results of analytical/empirical models and experimental results highlights the ability of various applied models to estimate the FRP contribution across various strengthening system variations, including varied amount of material, layout configurations, and choice of bedding mortar.