This study evaluated the mineral content of remineralized caries-affected dentin (CAD) using nano coral calcium versus nano coral calcium with chitosan and their effect on microshear bond strength (µSBS) to composite resin in relation to sound dentin. 50 teeth were randomly divided in which 20 dentin specimens were used for EDX evaluation; another 20 were qualitatively analyzed using FESEM. For the remaining 10, each tooth was cut into four quadrants obtaining 40 dentin specimens for µSBS evaluation. All dentin surfaces were subjected to four different surface treatments; group1: sound dentin, group 2: CAD, group 3: demineralized then nano coral calcium, group 4: demineralized then nano coral calcium with chitosan. EDX showed increase of Ca and P (wt%), Ca/P ratio in two remineralizing materials when compared to CAD, meanwhile close to that of sound dentin. Furthermore, µSBS showed the highest value with nano coral calcium followed by sound dentin, then nano coral calcium with chitosan and the lowest was CAD. FESEM confirmed these results. Nano coral calcium and nano coral calcium with chitosan showed promising results regarding the remineralization of CAD improving its µSBS to resin composite. Coral reefs, natural calcium sources, have positive impact in solving CAD clinical problem.