This study describes a facile method for preparing poly(4,4′-oxydiphenylene-pyromellitimide) (POPI)/TiO2 nanocomposites. 4,4′-Methylene diphenyldiisocyanate (MDI) was used as the surface modifier of TiO2 nanoparticles. MDI modified and/or unmodified TiO2 were added to a viscose solution of poly(amic acid) (PAA) prepared by reacting 4,4′-oxydiphenylamine and pyromellitic dianhydride (PMDA). Casting the homogenized mixture onto glass Petri dishes gave the corresponding thermally cured films of POPI/TiO2 and POPI/TiO2-MDI nanocomposites through cyclodehydration of the PAA precursor. Diffuse reflectance UV/vis spectroscopy (UV/vis DRS) indicated that two absorption maxima are developed in the spectrum of MDI-treated TiO2 at about 440 and 580 nm, as well as a slight red shift in the absorption maxima of POPI/TiO2 and POPI/TiO2-MDI nanocomposites compared to the neat POPI occurred. From XRD measurements the mean sizes of nano-TiO2 in TiO2-MDI, POPI/TiO2, and POPI/TiO2-MDI were found to be 27, 22, and 19 nm, respectively. According to the SEM images of POPI/TiO2 and POPI/TiO2-MDI nanocomposites, the nano-sized TiO2 particles with globular shapes were dispersed into the polymer matrix. According to the TGA/DTG thermograms it could be deduced that the incorporation of nano-TiO2 particles into the polymer matrix can lead to an appreciable thermostability. Taking into account, the DTA thermograms a discrete endothermic transition could be detected at about 290 ºC. MDI-grafted TiO2 seems to be a good candidate for incorporating into poly(4,4′-oxydiphenylene-pyromellitimide) as a commercial type polyimide.