The tacticity effects on the water-vapor sorption of the thin films of poly(N-ethylacrylamide) (PNEAm) and poly(N,N-diethylacrylamide) (PNdEAm) are investigated by the quartz crystal microbalance method and infrared spectroscopy. The quantity of sorbed water on the spin-coated films of isotactic-rich PNEAm is larger than that of atactic one. For PNdEAm, the syndiotactic-rich polymer film absorbs more water. The amide I or C=O stretching band of the polymers are monitored during water sorption on the spin-coated films. The result indicates that the water-sorption site is also influenced by the tacticity of the polymers. The annealing of these films wipes out the tacticity dependence of water sorption, indicating that the water-sorption sites in the spin-coated films are voids around C=O groups that are made by evaporation of solvent during spin-coating (so-called, the “solvent-imprint” effect). The isotactic-rich PNEAm is more influenced by the solvent-imprint effect than the syndiotactic-rich one, while an opposite tendency is found for PNdEAm.