In this study, calcium chloride-anodized alumina composites were examined for water vapor sorption properties. Porous alumina host matrices for calcium chloride impregnation were prepared by anodizing aluminum plates in an oxalic acid bath or a sulfuric acid bath. CaCl2-alumina composites were obtained through calcination of the anodic alumina film impregnated with a CaCl2 solution at 473 or 773 K. XRD analyses indicated that the type of host matrix and the calcination temperature made an effect on crystal states of calcium chloride in the composite layer. The composite calcined at 473 K, of which the host matrix was oxalic-acid anodized alumina film, contained calcium chloride anhydrate crystals. Water vapor sorption experiments showed that the composite with crystalline calcium chloride sorbed water vapor well, and its sorption isotherm had a shape similar to that of bulk CaCl2. Therefore, the water sorption behavior of the CaCl2-alumina composite strongly depends on the crystal states of calcium chloride in anodized alumina layer.