Untreated multiwalled carbon nanotubes (MWCNTs) were incorporated into a brittle epoxy matrix at 1 wt% by solvent evaporation and showed significant gains in tensile strength, strain at break, and electrical conductivity. However, only fractional improvement in fracture toughness was observed. To improve fracture toughness, 10 mu m polyamide-12 (PA) preformed particles were added at 20 wt% loading. The PA particles were observed to aid in the dispersion of MWCNTs, reducing most of the large MWCNT clusters to submicron sizes. The epoxy/PA/MWCNT ternary composite exhibits an increased electrical percolation threshold, but nearly identical electrical scaling behavior as the epoxy/ MWCNT composite. The similarity in percolation parameters suggest conduction occurs by efficient electron transport through MWCNT clusters, rather than pathways composed of individual tubes. The ternary composite also shows significant improvements in strain at break and fracture toughness due to synergistic interaction between filler phases. The usefulness of this ternary composite approach in vacuum-assisted resin transfer molding for advanced composite applications is discussed. POLYM. ENG. SCI., 51:2245-2253, 2011. (C) 2011 Society of Plastics Engineers