In this study, the effect of modified epoxide-terminated gamma-Fe2O3 on the magnetic, mechanical, and thermal properties of epoxy nanocomposite was investigated. The gamma-Fe2O3 nanoparticles were prepared via a wet chemical approach, surface modified with 3-glycidoxypropyltrimethoxysilane (GPTMS), and characterized by particle size analyzer, XRD, FT-IR, and TGA techniques. The catalytic effect of gamma-Fe2O3 on the cure reaction temperature of epoxy/triethylenetetramine (TETA) was determined by differential scanning calorimeter (DSC). The glass transition temperature (T (g)) of nanocomposite containing 5 wt% modified gamma-Fe2O3 increased slightly (12 A degrees C), while the initial decomposition temperature (T (ID)) did not show improvement. Transmission electron microscopy (TEM) showed improvement in dispersion of surface-modified gamma-Fe2O3 nanoparticles in the resin matrix. The effect of interfacial bonding between modified gamma-Fe2O3 and epoxy resin, via crosslink reactions, on the mechanical properties of nanocomposite such as flexural and tensile strength was studied, and the fractured surface of samples was investigated by scanning electron microscopy (SEM). Comparing with the mechanical properties of neat epoxy resin, tensile, and flexural strength of 10 wt% modified gamma-Fe2O3/epoxy nanocomposite increased 20 and 19 %, respectively, while tensile and flexural strength of 10 wt% unmodified/epoxy nanocomposite decreased slightly. The saturation magnetization (M (s)) of 5 wt% modified gamma-Fe2O3/epoxy nanocomposites with superparamagnetic property was approximately 80 % greater than that of unmodified gamma-Fe2O3/epoxy nanocomposites.