The aim of this work was to synthesize and evaluate a multifunctional chitosan - beta-glycerophosphate (?-GP) / hydroxyapatite - silica nanocomposite hydrogel for bone defect regeneration, so that to be injectable at room temperature, thermogelling at human body temperature, bioactive, biodegradable, local antibiotic releasing and facilitating bone regeneration. Phosphoric pentoxide, calcium nitrate tetrahydrate, and tetraethylorthosilicate were used as precursors for synthesis of hydroxyapatite - silica nanocomposite powder (reinforcement phase). Also, chitosan and ?-GP were used for synthesis of the matrix of the nanocomposite hydrogel. Obtained products were characterized by techniques such as X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDX), inductively coupled plasma optical emission spectroscopy (ICP), N 2 adsorption–desorption isotherms (BET), scanning electron microscopy (SEM), transmission electron spectroscopy (TEM), and UV spectrophotometer. Synthesized hydroxyapatite -10 Wt. % silica (HA-10S) nanocomposite powder in the presence of the acid catalyst with the most calcium ions release was selected as the optimized composition of the reinforcement phase. Results indicated the incorporation of SiO 4 4- into the hydroxyapatite tructure, and the creation of a discontinuous silica layer on its surface, which led to improve dissolution behavior and bioactivity of nanophase hydroxyapatite and also the increase of its resistance to dissolution in the acidic environment (2 M HCl). Investigation of the effect of the presence and the content of HA-10S in nanocomposite hydrogels showed that the presence of HA-10S in nanocomposite hydrogels led to a faint increase in physiological pH of based hydrogel (chitosan - ?-GP) and also its gelling time at 37°C decreased from 90 S to 60S. Moreover, the presence of HA-10S in nanocomposite hydrogels led to bioactivity and improvement of their mechanical properties and their biocompatibility. However, nanocomposite hydrogel including 10 Wt. % HA-10S nanocomposite powder (CH.?-10HA.10S) had the most elastic modulus and also precipitated apatite on its surface was more monotonous and more continuous. It was attributed to more homogenous distribution of HA-10S nanocomposite powder in the matrix of CH.?-10HA.10S. Investigation of ciprofloxacin release from nanocomposite hydrogels showed that they could release this drug into a controlled manner over a long period of time (more than two months) in phosphate buffered saline ( pH 7.4). Also, the entrapping of ciprofloxacin into the agglomerated HA-10S nanocomposite powder had an important role in decreasing its release rate and in increasing its period of release time.