Abstract: This study aims to evaluate the effectiveness of nanohydroxyapatite as a consolidating material for limestone monuments when dispersed in the SILRES® BS OH 100, compared to the polymer in individual form. The current study was applied to one of the stone artifacts displayed at the Obelisk Open Air Museum in El-Matareya, Cairo. Treated samples were subjected to accelerated aging by moisture, temperature and salts to evaluate the stability of the consolidants. Nanohydroxyapatite/ polymer nanocomposite was prepared using in situ emulsion polymerization system. TEM, SEM-EDX, PLM, XRD, colorimetric measurements, water contact angle, porosity, capillary water absorption measurements and compressive strength tests were used to evaluate the consolidants efficiency. The results of thin sections revealed that the studied limestone samples were very fine-grained (micrite) containing microfossils. XRD analysis proved that the archaeological limestone consists mainly of calcite with a small percentage of gypsum, while SEM examination showed the weakness and high porosity ratio of the archaeological limestone samples. However, SEM investigation proved that the samples treated with HAP/ polymer nanocomposite have a homogeneous coverage, and the consolidant was able to fill pores and provide good consolidation. Moreover, the physical and mechanical properties of studied limestone samples were significantly improved as a result of the use of HAP/ polymer nanocomposite after treatment and aging.