In recent years, carbon nanotubes (CNTs) have attracted a lot of interest as an additional component in fiber reinforced plastics (FRP) to improve the properties of the fiber/matrix interface. An improvement of the apparent interfacial shear strength (ISS) was achieved by grafting CNTs onto reinforcement fibers instead of dispersing CNTs in the matrix. In one study, composites containing CNT-grafted fibers and epoxy resin demonstrated 26% ISS improvement over the baseline composites. However, few studies are focused on glass fibers, due to their low heat resistance. In this study, the effects of grafting CNTs onto T-glass fibers were evaluated by investigating the mechanical and interfacial properties of the CNT-grafted fiber/epoxy resin model composites. Elastic shear-lag analysis was also used to investigate the effect of CNTs on ISS. We used the chemical vapor deposition (CVD) method to graft CNTs onto T-glass fibers. As a result, CNTs were grafted relatively uniformly and cylindrically onto the fibers, which indicates that the CNT-grafting process was appropriate. The CNT-grafted fiber/epoxy resin model composites showed a significant (46~67%) increase of interfacial shear strength. The formation of an interfacial region containing CNTs was observed around each fiber. Elastic shear-lag analysis showed a 20% increase of ISS. Those results imply that the elastic modulus of the interfacial region around the fibers was higher than that of epoxy resin.