Osteoporosis causes bone fractures and large irregular shape bone defects, which are usually treated with bone auto/allografts, inert metallic implants or bioactive ceramic implants. These approaches have numerous limitations, like insufficient availability, disease transmission, infection and brittleness. Therefore, there is a need for novel injectable, antibacterial, bioactive biomaterials for filling osteoporotic bone defects. The aim of this study was to synthesize and characterize composite hydrogels based on natural biopolymers ɛ-polylysine (ɛ-PL) and hyaluronic acid (HA), and strontium substituted hydroxyapatite nanoparticles (Sr-nHAp). The developed ɛ-PL-HA/Sr-nHAp composite hydrogel has great potential to be used as an injectable bioactive biomaterial for osteoporotic bone regeneration. Further studies need to be conducted on Ca2+ and Sr2+ ion release kinetics, cell viability and antibacterial activity to determine the full biomedical potential of this biomaterial.