Diglycidyl ethers of N,N’-bis(5-hydroxy-1-naphthyl)pyromellitimide (BNIDE) and polyethylene glycol (PEGDE) were binarily cured by N,N’-bis(5-amino-1-naphthyl)pyromellitimide (BNIDA) curing agent. Three homogenized mixtures of BNIDE and PEGDE resins with different mole ratios (75/25, 50/50 and 25/75) were isothermally reacted with the stoichiometric amounts of the curing agent. For comparison purposes, each diglycidyl ether was also cured separately with the same condition. The exothermic phase transitions associated with the curing processes were specified in the dynamic differential scanning calorimetry (DSC) traces of BNIDEBNIDA, BNIDE:PEGDEBNIDA, and PEGDEBNIDA mixtures. The completion of the curing processes was confirmed using Fourier transform-infra red (FT-IR) spectra and DSC traces of the isothermally cured resins. Effect of bis(naphthyl-imide) and polyoxyethylene units on thermal stability and T_g value of binarily cured epoxy resins was investigated by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Both thermal stability and T_g value of the imide-epoxy thermoset films significantly increases with BNIDE resin. Instead, when PEGDE resin was cured by BNIDA, the prepared films showed more flexibility and pliability. These important characteristics were appropriately balanced by employing three binary mixtures of BNIDE and PEGDE resins.