The addition of propolis extract (PE) to the glass ionomer results in an adhesive material for restorative treatment, with interesting properties mainly due to the flavonoids contained in the propolis extract. However, no study of the flavonoid release profile in these materials was reported. This work studies the flavonoid release profile in such materials aiming to contribute to the future synthesis of optimized devices adept to prolong the efficacy of the drug. The study involved the synthesis and study of the physicochemical, antibacterial and mechanical properties of glass ionomer cement (GIC) and glass-ionomer-propolis composites (GIC-PE). The samples were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analyses. The released concentration of flavonoids, the antimicrobial activity and the compressive strength were also evaluated. Antimicrobial activity was assessed against Streptococcus mutans, Streptococcus salivarius, and Candida albicans, common pathogens in the mouth. The results indicate that the antibacterial activity of GIC-PE samples is closely correlated with the release of flavonoids. The method used to prepare the composite GIC-PE leads to an initial drug delivery burst effect able to diminish partially the population of bacteria tested. The mechanical properties and thermal stability of GIC-PE are higher than those of the GIC and are clearly related to its microstructure. This study is clinically significant because the addition of propolis extract (PE) to the GIC resulted in a novel differentiated product with enhanced mechanical and antimicrobial properties compared to the GIC.