A new compatibilizer, poly(vinyl benzyloxy ethyl naphthalene)-graft-poly(methyl methacrylate), for poly(styrene-co-acrylonirile) (SAN)/multi-walled carbon nanotubes (MWCNTs) composites was synthesized. It has been identified that naphthalene unit in backbone of compatibilizer interacts with MWCNTs via pi-pi interaction and that the PMMA graft of the compatibilizer is miscible with the SAN matrix. When a small amount of compatibilizer was added to SAN/MWCNT composites, MWCNTs were more homogeneously dispersed in SAN matrix than the case without compatibilizer, indicating that the compatibilizer improves the compatibility between SAN and MWCNTs. As a consequence, mechanical and electrical properties of the composites with compatibilizer were largely improved as compared with those of composites without compatibilizer. (c) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4184-4191, 2010