Here we present bioinspired catechol-functionalized primers (catechol-spacer-methacrylate) for a tougher dental resin composite containing glass fillers. Catecholic primers with different end groups were designed and then coated on glass surfaces using a simple drop-casting or dip-coating process. The surface binding ability and possible crosslinking (coupling or chemical bridging between the glass substrate and the dental resin) of the catecholic bifunctional primers were evaluated using atomic force microscopy, contact angle measurements, and the knife shear bonding test and compared to a state-of-the-art silane-based coupling agent. Various mechanical tests including shrinkage and compression tests of the dental resin composites were also conducted. Compression tests of the composites containing the catecholic primed fillers exhibited enhanced mechanical properties, owing to the bidentate hydrogen bonding of catechol moieties to the oxide mineral surface.