This study aimed to compare the fluoride-releasing ability and degree of microbial attachment of a newly developed glass-hybrid restorative material (GH) with those of a high-viscosity glass ionomer (HvGIC), resin-modified glass ionomer (RMGI), and composite resin (CR). In addition, the correlation between fluoride-releasing ability and microbial attachment between materials was evaluated. Specimens were prepared in a disc shape and divided into 4 groups according to the materials (GH, HvGIC, RMGI, and CR). The fluoride release experiments were performed in each group (n = 15). The amount of fluoride released was measured on days 1, 3, 7, 14, 28, and 42 after storage. For the microbial attachment experiment, 12 specimens were produced per group using <i>Mutans Streptococci</i> (<i>S.mutans</i> ), a cariogenic microorganism. <i>S. mutans</i> was cultured on the specimens for 24 hours, and the number of bacteria was measured. GH had the highest cumulative fluoride release and showed a significant difference when compared with RMGI (<i>p</i> = 0.001) and CR (<i>p</i> < 0.0001). Microbial attachment was the lowest in GH; however, no significant difference was observed between the materials (<i>p</i> = 0.169). There was no significant correlation between fluoride release from materials and microbial attachment (<i>p</i> > 0.05). From this perspective, remineralization of low-mineralized areas could be expected due to the high fluoride release of GH, and the effect of delaying the progression of dental caries could be predicted from the low cariogenic microbial attachment. Therefore, GH might be a useful restorative material for treating immature permanent teeth with hypomineralized enamel. However, further studies are needed about the degree of remineralization of hypomineralized areas after restoration and the capacity to recharge fluoride.