Nanoparticles (NPs), such as metal oxides, have a strong tendency to agglomerate, so homogeneous dispersion of these materials in a polymer matrix is desirable. As a result to overcome this problem and to enhance the filler-polymer interaction, it is better to functionalize the surface of NPs. In this study we describe the synthesis and characterization of novel poly(amide-imide)/TiO2 nanocomposites (PAI/TiO2 NCs). At first, the surface of TiO2 NPs was modified by N-trimellitylimido-L-valine as a bioactive coupling agent. Modification by this linker causes that, the obtained TiO2 NPs become environmentally friendly. Thereafter, NCs of modified TiO2 and PAI were synthesized by means of an ultrasonic technique. PAI as a source of polymer matrix was synthesized by direct polycondensation reaction of N-trimellitylimido-L-valine with diaminediphenylsulphone in the presence of triphenyl phosphite and the molten tetra-n-butylammonium bromide. By the insertion of surface modified TiO2 NPs into the polymer matrix, a considerable improvement of thermal property was achieved which was examined using thermogravimetric analysis. The structure and morphology of resulting NCs with 5 %, 10 % and 15 % TiO2 NPs were characterized by Fourier transform IR spectroscopy, X-ray diffraction, Field emission scanning electron microscopy and transmission electron microscopy. The optical properties of the NCs were studied using ultraviolet–visible spectroscopy.