Gastroresistant capsules are obtained mostly by using modified-release fill in hard capsules, or by coating the gelatin shell with acid-resistant polymers. Modification of the material used at the stage when the capsule shell is produced would reduce the complexity and cost of introducing new products to the market. Gastroresistant gelatin films were obtained by using commercial cellulose acetate phthalate (aqueous dispersion Aquacoat® CPD). Only films casted from non-alkalized mixtures showed no visible disintegration at pH from 1.2 (simulated gastric fluid) to 4.5 (phosphate buffer). Elasticity of the dry films was comparable with the one determined for non-modified gelatin films, however tear resistance was 2-fold smaller, but still acceptable for practical application.