The electrical conductivity of ternary composites composed of a biopolymer blend with conductive particles (carbon black (CB)) is enhanced by the selective localization of CB depending on the concentration of a secondary phase (poly(caprolactone) (PCL)) when the CB particles have higher chemical affinity to the secondary phase relative to the matrix (poly(lactic acid) (PLA)). As the content of the PCL phase decreases to 4wt%, the PCL phase induces the aggregation of CB particles, resulting in a shift of the particle percolation threshold to a lower concentration of particles. Moreover, the mixing ratio between CB and PCL considerably affects the percolation of particles. When the mixing ratio of CB to PCL is equivalent (1:1), the ternary composite with PCL-induced CB aggregates shows high electrical DC conductivity above 1 S/m with 10 wt% CB. The addition of a small amount of PCL induces the formation of particle aggregates with a high aspect ratio, providing more electron transfer pathways due to the multiple contact points between the aggregates. Meanwhile, a binary composite (PLA/CB) never reaches high electrical conductivity of 1 S/m and even requires a further concentration of CB (13 wt% CB for 10-3 S/m) to accomplish electron transfer because of the small aspect ratio of randomly-dispersed particle aggregates.