The effects of saturated fatty acids at a concentration of 1.5% on the mechanical and barrier properties of starch-based films were evaluated in films prepared with two concentrations of glycerol, 20 and 25%. The water vapor permeability (WVP) was determined at three ranges of relative humidity, RH, (033, 3364 and 6497%). In all cases, an increase in WVP values was observed with increasing RH. SEM images showed a more homogeneous and compact structure in the films with caproic and lauric acids. The films with fatty acids showed higher elongation and maximum stress, and they had Young's modulus values close to those of the control; thus, the addition of fatty acids did not impair the mechanical properties. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012