Romania has a significant number of historical monuments that have been damaged or degraded due to earthquakes or lack of maintenance during the communist period (1945–1990). After the 1989 Revolution, several historical buildings, mainly single-story structures, underwent consolidation using irreversible methods and technologies that contradicted the principles of the Venice Charter. These techniques, which primarily involved reinforced concrete, in some cases exacerbated physical deterioration due to the differing physical-mechanical properties between historic hydraulic lime masonry and reinforced concrete. Moreover, interventions using reinforced concrete altered the rigidity of historical buildings, exposing them to seismic forces greater than those they had endured over centuries. However, the irreversible use of reinforced concrete was impossible for Orthodox churches classified as historic monuments, as they feature interior and exterior wall paintings as well as frescoes on vaults or domes. This article presents strengthening solutions that utilized composite materials produced by the Kerkoll company in the consolidation of the Church of St. Philimon Monastery in Vătășești, Vâlcea County, Romania. A significant advantage of using composite materials is the incorporation of sustainable materials, such as hydraulic lime and basalt mesh, which reduced humidity levels within the church while increasing its seismic load-bearing capacity without altering its original rigidity. The use of composite materials ensured the spatial cooperation of all structural walls, the transfer of thrust forces from vaults and domes, and the overall stability of the walls. In conclusion, this article highlights the multiple advantages of using composite materials in the strengthening of historic churches from an artistic, structural, and sustainability perspective.