In this morphological study the dispersion and localization behavior of 1 wt.% graphene nanoplatelets (GnPs) in melt mixed co-continuous polymer blends of polycarbonate (PC, 59 wt.%) and poly(styrene-acrylonitrile) (SAN, 40 wt.%) were investigated. Through varying the mixing sequence as well as the melt mixing parameters, different states of dispersion and different filler localizations were achieved. Melt mixing in a one-step process resulted in the poorest dispersion of the GnPs in the polymer blend. In this case, the filler could hardly be found localized selectively in one of the polymer components but formed its own component. In two-step mixing processes the GnPs were either premixed in PC or SAN to investigate the assumed filler transfer from the SAN into the PC component. Four different premixtures were prepared which showed that longer mixing time and higher rotation speed resulted in better dispersion of the GnPs in the polymer matrix. If the GnPs were predispersed in PC they could still be found in the PC component after blending with SAN. In the case that the GnPs were premixed in SAN, the filler was detected partially in the SAN or at the blend interface, as well as smaller sized particles were found in the PC component. It could be shown that the size and aspect ratio of the filler play a significant role on the localization of GnPs in melt mixed polymer blends. (C) 2013 Elsevier Ltd. All rights reserved.