Tissue engineering and regenerative medicine has been providing exciting technologies for the development of functional macroporous biomaterials (scaffolds) aimed to repair and regenerate damaged bone. Biodegradability, high mechanical strength, osteointegration and formation of bony tissue are properties required for such materials. Bioactive synthetic hydrogels have emerged as promising materials because they can provide molecularly tailored biofunctions and adjustable mechanical properties, as well as an extracellular matrix-like microenvironment for cell growth and tissue formation. In this study, injectable composite hydrogels were designed to be used in bone tissue regeneration. To mimic the mineralogical and organic components of the natural extracellular matrix of bone, hydroxyapatite and a tyramine conjugate of gelatin were combined to manufacture the composites. Gelatin conjugate is able to crosslink through the oxidative coupling of tyramine molecules, catalyzed by hydrogen peroxide and horseradish peroxidase, via non-cytotoxic conditions. The effect of various amounts of in situ synthesized hydroxyapatite in gelatin-tyramine solutions was investigated by analysing the morphology and physical properties of the resulting hydrogels. Characterization of hydroxyapatite within the hydrogels was performed by X-ray diffraction analysis and Fourier transform infrared spectroscopy. The morphology of prepared hydrogel was characterized using scanning electron microscope. Shear storage and loss moduli were measured as a function of gelation time, while the rheological properties of the completely crosslinked hydrogels were tested by changing the shear strain and frequency. Results have confirmed adequate formation of apatite within the gelatin-tyramine matrix. Microscopy reveals better dispersion of hydroxyapatite crystals by in situ synthesis than in control samples prepared by classical blending. The rheological testing has shown no significant effect of hydroxyapatite content on the gelation time with respect to pure gelatin-tyramine matrix, while shear strength of the different hydogels seems to needs to be further investigated.