Fiber reinforced cementitious mortar (FRCM) systems, innovative strengthening systems, for repairing and strengthening concrete and masonry structures are an alternative option to traditional techniques such as fiber reinforced polymers (FRPs), steel plated bonding, and section enlargement. In this paper, a FRCM strengthening system made of polypara phenylene benzobisoxazole (PBO) fiber mesh embedded in cementitious matrix and bonded to concrete is investigated. There are two main parts in this paper: (i) the effective bond length of PBO mesh in PBO-FRCM system and (ii) the bond stress-slip relationship between PBO mesh and concrete substrate. An experimental program of single pull-out shear tests for the PBO-FRCM system is designed and conducted to verify the above two purposes. The results of this study can be used to estimate the effective bond length of PBO mesh in PBO-FRCM systems and also investigate if the debonding phenomenon occurs in the cementitious matrix or at the fiber and matrix interface. The comparison between the PBO-FRCM system and the ordinary FRP system is also discussed.