Alumina nanoparticles were functionalized with 3-glycidyloxypropyl trimethoxysilane for compatibility with a low viscosity bisphenol E cyanate ester (BECy) resin. The functionalized alumina nanoparticles were characterized with Fourier transform infrared and thermogravimetric analysis. The alumina nanoparticles, which increase the viscosity of the BECy/alumina suspension, show a concurrent catalytic effect on the cure of the BECy resin, as indicated by reduced gelation times under isothermal cure conditions. Transmission electron microscopy micrographs reveal that most of the alumina nanoparticles are well dispersed in the BECy matrix, but a small fraction of particles formed agglomerates. The thermal-mechanical properties of cured BECy composites reinforced with either bare alumina or functionalized alumina are evaluated by dynamic mechanical analysis. The storage modulus increases with both bare and functionalized alumina loading. Although the glass transition temperatures (T-g) of bare and functionalized alumina/BECy nanocomposites decrease with increasing filler content, the reduction in T-g is less severe when the alumina nanoparticles are first functionalized. POLYM. ENG. SCI., 50:302-311, 2010. (C) 2009 Society of Plastics Engineers