Synopsis: Fiber reinforced cementitious mortar (FRCM) systems present a novel means of strengthening deficient concrete structures. They present a number of advantages over conventional externally bonded fiber reinforced polymer (FRP) systems. FRCM systems consist of open-weave polybenzoxozole (PBO) fabrics which are applied to structural elements, walls, domes, tunnels, or shells using cementitious mortars. They are breathable, non-combustible and non-flaming, and their performance in elevated service temperature environments is superior to common FRP systems. However, additional research on FRCM is needed, most importantly on their high temperature performance and their long term durability, before they can be widely applied with confidence. This paper reports on an ongoing experimental study into the performance of a specific FRCM system for concrete. Comparative tests on FRCM and FRP strengthened concrete prisms are presented. The superior performance of FRCM strengthening systems at temperatures between 50°C (122°F) and 80°C (176°F) is demonstrated. The effects of elevated service temperature environments on the bond between FRP strengthening systems and concrete are discussed.