Investigations on the preparation of controlled-release fertilizer coated with polymers, have been described. The polymer materials used were polysulfone (PSF), cellulose acetate (CA) and polyacrylonitrile (PAN). The polymer coatings were formed on the granular NPK fertilizer by the phase inversion technique. The measurements of thickness and porosity of prepared coating and microphotographic observation of the coating were performed. The thickness of fertilizer coatings, measured by the micrometer screw was in the range from 0.21-1.14 mm - depredating on the polymer type. It was found, that a higher concentration of polymer in film forming solution causes a decrease of the porosity of the obtained coating. The microphotographs of the coatings obtained for this study demonstrate that the prepared coatings in all cases were asymmetric with thin skin layer formed on the top of the coating. The polymer coatings were characterised using Fourier transform infrared spectroscopy (FT-IR). The coatings, formed on the fertilizer, were compared with coatings prepared from the same polymer but without the contact with fertilizer. It was observed that the spectra of pure polymer showed the peaks with lower intensity.