Electrically conductive polycarbonate (PC) nanocomposites are prepared by blending PC with thermally exfoliated graphene and p-phenylenediamine (PPD)-functionalized and reduced graphene oxide (GO-PPD). The filler dispersion in the PC matrix is evaluated with scanning electron microscopy, transmission electron microscopy, and rheological measurements. Compared to thermally exfoliated graphene, GO-PPD exhibits a better compatibility with the PC matrix and thus a more homogeneous dispersion due to the presence of PPD in GO-PPD. After being freely foamed with supercritical carbon dioxide as the foaming agent, the PC/GO-PPD nanocomposite foams show improved cell structures with higher cell density, smaller cell size, and more regular shapes; these should be attributed to the uniform dispersion of GO-PPD sheets in the matrix, which act as nucleation sites for foaming. Interestingly, the conducting network formed by GO-PPD sheets survives even after mold-limited foaming of PC/GO-PPD nanocomposites, and therefore the nanocomposite foams exhibit similar or even higher electrical conductivity in comparison to their solid counterparts.