Carbon nanotubes (CNTs) are used as conducting nanoscale fillers to enhance the electrical performance of polymer nanocomposites due to their outstanding electrical properties, but they exist as bundles caused by strong van der Waals force between them. A lot of works such as physical and chemical modifications of CNTs have been performed to solve the dispersion problem. Chemically modified CNTs show good dispersion but deteriorate the intrinsic properties of CNTs by the breakage of sp2 bond. Physical modification with low molecular weight surfactant renders good dispersion but shows adverse effect on mechanical properties of nanocomposites. In this study, polystyrene (PS)/surface-modified CNT nanocomposites were prepared by latex technology, and then the rheological and electrical properties of nanocomposites were investigated to compare the effect of surface-modified CNTs. Polydopamine coated CNTs (PDA-CNT), poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) coated CNTs (PEDOT:PSS-CNT), ethylene glycol treated PEDOT:PSS-CNTs (EG-PEDOT:PSS-CNT) and sodium dodecyl sulfate stabilized CNTs (CNT/SDS) were used as nanoscale fillers. PDA-CNT was prepared by spontaneous oxidative polymerization under tris-HCl buffer solution of pH 8.5, and not only PEDOT:PSS-CNT but also EG-PEDOT:PSS-CNT was prepared by π-π stacking interaction between PEDOT:PSS and CNT. Good dispersions of surface-modified CNTs in aqueous system were achieved. As a result, rheological properties of each nanocomposite were highly enhanced with the content of the CNTs, leading to rheological percolation thresholds less than 1 wt%. Electrically conducting pathway for PS/PDA-CNT, PS/PEDOT:PSS- CNT, PS/EG-PEDOT:PSS-CNT and PS/CNT/SDS nanocomposites was achieved at the electrical percolation threshold of 0.58, 0.32, 0.40 and 0.18 wt%, respectively.