Novel Acrylonitrile Butadiene Styrene (ABS) materials melt-blended with 5 wt. % and 10 wt. % XGnP™ M5 graphene nanoplatelets were fabricated into 1.75 mm diameter filament for 3D printing in order to ascertain how strength and toughness of 3D-printed ABS may be affected by M5 addition. An ABS with a bimodal molecular weight distribution with a prominent portion of the distribution at the low MW end was selected in order to foster early stage interdiffusion between and interfilament adhesion of the printed filaments. The ABS samples were thoroughly characterized for molecular weight, styrene and acrylonitrile (AN) levels, rubber content (via 1H NMR and 13C NMR), and melt rheology. Material and 3D printing variables were assessed. Accessible print speed was limited by melt viscosity of the melt blends. 3D printing patterns (0 deg. axial and 45/45 deg. bead raster angles) were selected in order to determine their influences on toughness, tensile and dynamic mechanical properties. Toughness was halved with graphene with each 5 wt. % addition of graphene, while tensile modulus roughly doubled with increasing graphene content from 0 wt. % to 10 wt. % M5. The 45-45 deg. 3D printing configuration affected little change in notched Izod toughness vs. the 0 deg. axial printing configuration. Test bars fabricated to shape by 3D printing were compared with analogous bars milled to the identical shape to measure the differences in the resulting physical properties. Generally, the properties for print-to-shape tensile samples were found to be inferior to the milled-to-shape equivalents due to circumferential printing paths that formed planar weaknesses at the sample edges.