In this study, injectable pastes based on a clinically-tested bioactive glass and glycerol (used as organic carrier) were produced and characterized for further application in regenerative medicine. The paste preparation route, apatite-forming ability in simulated body fluid (SBF) solution, viscoelastic behavior and structural features revealed by means of scanning electron microscopy (SEM), FTIR and Raman spectroscopy were presented and discussed, also on the basis of the major experimental data obtained in previous studies. A mechanism illustrating the chemical interaction between bioactive glass and glycerol was proposed to support the bioactivity mechanism of injectable pastes. Then, the results of In vivo tests, conducted through injecting moldable paste into osseous defects made in rabbit’s femur, were reported. Animal studies revealed good osteoconductivity and bone bonding that occurred initially at the interface between the glass and the host bone, and further supported the suitability of these bioactive glass pastes in bone regenerative medicine.