This study aimed to investigate the effects of inclusion of Al2O3-doped bioactive glass (BG) and silane treatment on physical properties and bioactivity behavior of resin-based experimental dental composites (EDCs). Melt-derived 45S5 BG and alumina doped 45S5 BG were prepared and incorporated into EDCs with and without silanization. EDCs prepared were subjected to three-point bending, microhardness, water sorption (WS), solubility (S), and bioactivity tests. Using non-silanized Al2O3-doped BG in EDCs resulted in improved flexural strength (FS), flexural modulus (FM), and microhardness and decreased bioactivity compared to EDCs containing non-silanized BG. There was no significant difference (p < 0.05) between WS and S results of non-silanized glass containing EDCs. Using silanized BG and Al2O3-doped BG resulted in improved FS and FM, decreased WS, S, and bioactivity. Addition of Al2O3-doped BG as a possible bioactive filler to EDCs improved mechanical performance while slightly decreasing bioactivity compared to BG containing EDCs.