This study investigated the physical properties of section-restoration mortar with calcium nitrite and carbon dioxide (CO2) nanobubble mixing water to develop materials and methods for the repair and reinforcement of cracks in reinforced concrete (RC) structures. As the calcium nitrite content increased, the generation rate and generated amount of nitrite-based hydration products increased, owing to the rapid reaction between NO2- ions in calcium nitrite and C3A(Al2O3). Further, the reaction with C3S and C2S was accelerated, thereby increasing the generation rates of Ca(OH)2 and C-S-H. Further, the large amount of Ca2+ ions in these hydration products reacted with CO32- ions in CO2 nanobubble water, thereby increasing the generation of calcite-based CaCO3 in the cement matrix. This appears to have affected the strength development and durability improvement via the densification of the structure. These results suggest that the performance of polymer cement mortar for repairing concrete structures can be improved if calcium nitrite and CO2 nanobubble water are properly combined and applied.