Aminated lignin possessing significant amount of reactive amino groups was studied as a curing agent of epoxy resin. Fourier transform infrared spectroscopy results proved the reactivity of the aminated lignin with the epoxy resin. Both appearance features and scanning electron microscopy images indicated that the transparent and homogeneous epoxy resin films could be formed with the aminated lignin less than 40% in the hardener mixture. In addition, thermogravimetric analysis and dynamic thermomechanical analysis results revealed that the epoxy resin cured by aminated lignin had better thermal stability compared with ones cured by a common hardener. The mass loss of the epoxy resin cured by the aminated lignin before 300 degrees C was small around only 2.5%. The T-g (the glass transition temperature) of epoxy resin sample after cured by mixed hardener increased from 79 degrees C to 93 degrees C. The obvious difference (70-84 degrees C) of T-d (the thermal deformation temperature) was also observed from the samples with and without the aminated lignin after cured at a high temperature. POLYM. ENG. SCI., 55:924-932, 2015. (c) 2014 Society of Plastics Engineers