A moistureproof cellulose ester film which has satisfactory optical performances, excellent moisture permeability, and excellent dimensional stability; and a protective film for polarizers which comprises the film. This moistureproof cellulose ester film comprises: a cellulose ester film and, deposited on at least one side thereof in the following order, one or more adhesion layers each having a carbon content in terms of atom number concentration of 1-40% and comprising an inorganic compound as the main component, one or more barrier layers each having a carbon content in terms of atom number concentration of 0.1% or lower, comprising silicon oxide as the main component, and having a film density of 2.16-2.60, and one or more protective layers each having a carbon content in terms of atom number concentration of 1-40% and comprising an inorganic compound as the main component. The total thickness of these deposit layers on one side is 1-100 nm. It is characterized in that the barrier layers on one side have a thickness of 0.1-30 nm.