There is substantial need to strengthen heat-damaged concrete. One possible method is to retrofit the concrete with fiber reinforced polymer (FRP) composites. However, the heat-damaged concrete may express poor performance in bond between FRP and concrete. To overcome this issue, externally bonded reinforcement on grooves (EBROG) method was investigated in this study to improve the bond behavior of carbon FRP sheets to heat-damaged concrete. Concrete blocks were initially exposed to elevated temperatures by using a pre-defined heating protocol. Externally bonded reinforcement (EBR) method and EBROG method were utilized to strengthen the heated concrete. Single lap shear experiments were performed on FRP-retrofitted post-heated concrete specimens. Experimental results demonstrated that using EBROG method significantly improved the bond behavior, compared to the EBR method. More importantly, the groove dimensions affect the bond strength. By using different groove depths of 5, 10, and 15 mm, the maximum bond strength was experienced for depth of 10 mm.