The effects of methanol and ethanol vapor-induced crystallization on vapor and gas permeabilities and on the structure of poly(lactic acid) (PLA) films were systematically investigated. At high temperature conditions, the vapor permeability of PLA films decreased with increasing exposure time. The PLA films that were exposed to alcohol vapor became slightly cloudy, and no changes in chemical structure were observed. Alcohol vapor-induced crystallization formed α-crystal structure. The vapor permeability decreased with increasing crystallinity. However, nitrogen permeability slightly increased after vapor-induced crystallization. The dependence of crystallinity on vapor and gas permeabilities was different from each penetrant. Total crystalline structures, including continuous crystal structures, remaining amorphous regions, and their interface depend on vapor and gas permeabilities. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40140.