In this study, the preparation of hydroxyapatite nanoparticles (HA NPs) from eggshells were carried out using chitosan nanoparticles (CS NPs) for the incorporation of urea fertilizers. The interaction and stability of HA NP/CS NP suspensions containing urea fertilizer were evaluated by FTIR spectroscopy, X-Ray diffraction (XRD), particle size and shape analysis by transmission electron microscopy (TEM) and composition by EDX. The synthesized HA NPs/CS NPs and HA NPs/CS NPs loaded with urea fertilizer after dissolved in water for 6 h with sizes as small as respective ~30-55 nm and ~50-90 nm were achieved. The obtained nanoparticles had a homogeneous morphology showing a quite uniform particles size distribution with a spherical shape. The mean diameter increase of the HA NPs/CS NPs in suspension with the addition of urea indicated that the elements are being aggregated and loaded on the surface of urea fertilizers.