Tissue Engineering is a potential alternative to the conventional methods for bone tissue regeneration. For this reason, investigated materials could replace existing non-degradable materials with no possibility of simultaneous tissue regeneration and degradation themselves. "Smart" materials have the ability to change the physical properties responding to environmental changes. Due to mentioned, they are used in biomedicine and bioengineering. Temperature sensitive polymers are used in tissue engineering as substrates for cell growth and as injectable gels. Injectable gels can be applied directly at a desired location in a minimally invasive manner. Injectable gels are used for delivery of cells, nutrients and growth factors to the three-dimensional structure in the body, and designed for gelation under physiological conditions. Injectable hydrogels based on chitosan as a biodegradable polymer matrix and hydroxyapatite as a bioactive inorganic phase are prepared in this study. Gelling of composite hydrogels has been initiated by decomposition of sodium hydrogencarbonate (NaHCO3) as a gelling agent. The hydrogels’ composition was determined by X-ray diffraction analysis and Fourier transmission spectroscopy. The morphology of hydrogels was investigated by scanning electron microscopy. Storage and loss shear modulus are determined by time sweep test, while rheological behaviour of physically cross-linked hydrogels was investigated by amplitude and frequency sweep experiments. Biological characterization was carried out by evaluation of hydrogel’s cytotoxicity on mouse fibroblast cells, and by determination of viability of mouse fibroblasts encapsulated within the hydrogel for 7 days of culture. The characterization of prepared hydrogels has confirmed hydroxyapatite formation within chitosan matrix with coexistence of octacalcium phosphate phase. Microscopic analysis reveals highly porous hydrogel’s structure confirmed by high water content of 97.5 ± 0.04%. The rheological measurements have indicated rapid thermogelling within 3 minutes of incubation at 37 °C, and formation of 'strong physical gel' with increment of shear storage modulus by shear deformation. High viability of fibroblast cells indicates non-cytotoxicity of hydrogels. In vitro culture of encapsulated fibroblasts has confirmed good cell viability during 7 days.