Calcium hydroxide cement (CHC), which is a direct pulp-capping material, has been widely used for several decades. In spite of the well-known advantages of CHCs, they have some disadvantages as well, such as high solubility, no inherent adhesive qualities, and low mechanical strength. Previous studies were undertaken to improve these deficiencies by implementing changes to modify the conventional CHCs. The aim of the present research is to demonstrate the potential rectification of the aforementioned deficiencies of the commercially available CHCs by adding hydroxyapatite (HA) nanoparticles without lessening their advantages. Here, the synthesized HA nanoparticles were added into the CHCs in two different portions of 3 and 7 wt%. A scanning electron microscope was used to observe and analyze the microstructure, and X-ray energy dispersive analysis was used to analyze the elemental composition of the new CHCs. In addition, setting time, mechanical strength, pH, calcium (Ca) release, and antibacterial behavior were measured to assess how HA nanoparticles influence the characteristics of CHCs. The results showed that adding 3 wt% HA nanoparticles can optimally improve the mechanical strength of the cement and increase the Ca release rate as a mineralization promoter without reducing the antibacterial behavior.