The clinical applications of glass ionomer cements (GICs) are limited by their relatively poor mechanical properties and insufficient remineralizing capacity. In this study, we developed hybrid GICs with improved mechanical and remineralizing properties via incorporation of an optimum amount (5 wt%) of 45S5 bioglass-ceramic particles. Also, we found that bioglass-ceramic particles with 74% crystallinity best act as both remineralizing and reinforcing agents. The degree of crystallinity of the additives, is overlooked in this context in other research. At around 74% crystallinity, there is sufficient amount of combeite and an amorphous phosphorous-rich phase in the 45S5 bioglass-ceramic particles to respectively promote their reinforcing role and allow them to effectively partake in the setting process creating an excellent interfacial bond with the GIC matrix. As a result, several strengthening mechanisms such as crack deflection and crack-tip shielding are activated within the hybrid GIC containing 5 wt% bioglass-ceramic with 74% crystallinity, contributing to its improved mechanical properties. The enhanced remineralizing and mechanical properties of such hybrid GICs can potentially improve their in vivo performance and broaden their clinical applications.