Masonry arches are an important part of built heritage that must be preserved. Research and advanced studies of historical masonry structures have progressed slowly in comparison to studies on structures made of other materials (e.g., concrete, steel), resulting in a lack of knowledge and experience in this field. This research evaluates the effectiveness of basalt textile-reinforced mortar (BTRM) as a compatible strengthening composite material for stone masonry arches, providing researchers with further quantitative data. To do so, 11 masonry arches were constructed, strengthened with different layouts, and tested. Furthermore, the BTRM was characterized by testing its constituent materials and the composite material. Once analyzed and compared with other studies, the results showed that BTRM is a promising solution for strengthening stone masonry arches. It is easy to apply, compatible and gives the original structures greater mechanical properties, in terms of ultimate load and deformation capacity.