Nanocomposites have attracted much attention from scientific and industrial areas in recent decades because of their mechanical, physical, thermal and barrier properties and unique design possibilities. These materials have been commercially used in the automotive, electronic, biomedical, packaging etc. industries and their usage areas have been increasing day by day. In this study, nanocomposite adhesives were produced by adding nano graphene and multi-walled carbon nanotube (MWCNT) particles to a single component epoxy adhesive at the ratios of 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 1, 3 and 5 wt.-%. Then, these nanocomposite adhesives were used to prepare single-lap joints. Shear tests were performed to specify their adhesive shear strengths and joint tensile strengths. It was observed that mechanical strength increased to the reinforcement amount of 0.5 wt.-%. After that, the strength values decreased due to a tendency towards agglomeration, viscosity increment and due to a difficulty in homogeneously applying the adhesive. Furthermore, it was found that nano graphene reinforcement improved the mechanical strength of the epoxy-based adhesive slightly more than MWCNT reinforcement.