In this paper, the structural behavior under lateral load of a masonry-barrel vault, strengthened by new technology by applied Carbon-Fiber Reinforced Polymer (C-FRP), is discussed from both theoretical and experimental points of view. The C-FRP is applied such as to assume an Ω shape around a concrete core at the vault extrados. A theoretical prediction of ultimate strength was derived in agreement with observations during the experiments (e.g., masonry crushing, FRP rupture, debonding, sliding along the mortar joint). A lower-bound limit-analysis approach was developed that can handle the shear strength of each ideal section given by the Mohr-Coulomb friction law (for the mortar joint). It can also handle other non linear Italian Code relations (for CFRP Ω-Wrap reinforcement) at a given level of normal compressive stress resulting from the previous step.