it was evaluated the morphological surface of thermoplastic starch (tps) obtained from three modified cassava starch varieties, plasticizer and an antimicrobial agent. the films was made by blown extrusion and extended over a slide and then was taken photomicrographs with 4x and 10x objectives. it was used high resolution optical microscopy to image characterization. the technique showed the effect of plasticizer addition over the starch films microstructure, it was found some inhomogeneity; however was identified some smooth regions related to form and size of starch granule, plasticizer concentration and extrusion variables process like velocity screw and temperature profile. this research contributed to characterize microstructural properties and gave some insights about the mechanical behaviour of tps films, needed to study and make biodegradable films.