To obtain homogeneous dispersion and good interfacial interaction between MWCNT and polymer matrix, the functionalization of MWCNTs with 3,5-diaminobenzoic acid (DAB) via a direct Friedel-Crafts acylation was accomplished. FTIR, XPS, and FT-Raman analysis was performed to confirm that diaminobenzoyl moieties were successfully grafted onto MWCNT surface with less structural damage. The incorporation of diaminobenzoyl-functionalized MWCNTs (DAB-MWCNTs) into epoxy matrix can substantially enhance storage modulus (E) as well as glass transition temperature (T-g) and reduce the coefficient of thermal expansion. The thermal conductivity enhancement can be observed with DAB-MWCNTs probably due to good dispersion and decreased interfacial thermal resistance between MWCNT and polymer matrix. The Maxwell-Eucken, Lewis-Nielsen, and MG-EMA models were used to evaluate theoretical thermal conductivity. Moreover, epoxy resin incorporated with hybrid fillers, which consisted of DAB-MWCNTs and silicon nitride exhibit higher thermal conductivity than those with single filler, thereby forming perfectly heat conductive pathways. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3184-3196, 2013