The aim of this research was to investigate nanostructures of chitosan (CS)/poly(ethylene glycol) (PEG) blend films. Solution blending was used to prepare CS/PEG blends before film casting. The blend films with CS/PEG ratios of 32/1, 16/1, 8/1, 4/1 and 2/1 w/w were investigated. Intermolecular interactions between CS and PEG of the blend films were observed from their FTIR spectra. Film morphology was studied from scanning electron micrographs. Nanopores were observed on the both film cross-sections and surfaces throughout the film matrices. The closed nanopores have firstly detected on the film cross-sections of the 32/1 CS/PEG blend film, whereas the film surfaces showed nanopores when the CS/PEG ratio was decreased to 4/1 w/w. The blend films with CS/PEG ratios of 4/1 and 2/1 w/w were nanoporous films. Finally, film transparency decreased and moisture uptakes increased as the PEG blend ratio increased.