To improve the thermal and mechanical properties and further to expand its applications of epoxy in electronic packaging, reduced graphene oxide/epoxy composites have been successfully prepared, in which dopamine (DA) was used as reducing agent and modifier for graphene oxide (GO) to avoid the environmentally harmful reducing agents and address the problem of aggregation of graphene in composites. Further studies revealed that DA could effectively eliminate the labile oxygen functionality of GO and generate polydopamine functionalized graphene oxide (PDA-GO) because DA would be oxidated and undergo the rearrangement and intermolecular cross-linking reaction to produce polydopamine (PDA), which would improve the interfacial adhesion between GO and epoxy, and further be beneficial for the homogenous dispersion of GO in epoxy matrix. The effect of PDA-GO on the thermal and mechanical properties of PDA-GO/epoxy composites was also investigated, and the incorporation of PDA-GO could increase the thermal conductivity, storage modulus, glass transition (Tg), and dielectric constant of epoxy. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39754.