Polyimide nanoparticles were obtained by the heterophase polycondensation of different aromatic tetracarboxylic acids and diamines in imidazolium-based ionic liquids (IL) as continuous phase. Because of the amphiphilic character of the IL, no additional surfactant is required for the stabilization of the employed dispersions. The low vapor pressure and high thermal stability of the reaction medium allow the use of high temperatures needed for the condensation reaction. The reaction takes place without commonly added extra components like LiCl or pyridine. The obtained polyimide was characterized by IR spectroscopy and gel permeation chromatography (GPC). Electron microscopy (TEM and SEM) shows a homogeneous morphology of the nanoparticles.