The state of dispersion of two types of graphite nanoplates, namely graphene nanoplates (GnPs) and expanded graphite (EG), in polycarbonate (PC)/poly(styrene-acrylonitrile) (SAN) = 60/40 wt.% blends prepared with a two-stage melt-mixing approach is investigated and its influence on the melt rheological and electrical properties is evaluated. By using two different parameter sets in the first mixing step, different states of the filler dispersion are achieved in the PC. After mixing with SAN, the more stringent premixing conditions (higher mixing speed and longer mixing time) resulted in a lower proportion of visible graphitic structures. The EG achieved a better dispersion than the GnPs. The electrical conductivity is lower for each filler type when the samples show a better dispersion. On the other hand, a better dispersion led to a higher reinforcing effect (as observed in melt rheological studies). By determining the shear dilution exponent and applying the Eilers equation to the rheological results, the strengthening effect and the differences in the state of the filler dispersion between the two premixing conditions were evaluated.