Disclosed is a polarizing plate protective film having high dimensional stability against moisture. Also disclosed are a polarizing plate using such a polarizing plate protective film, and a liquid crystal display. Specifically disclosed is a polarizing plate protective film which is characterized by containing a cellulose ester and a polymer X which is obtained by copolymerizing at least a styrene derivative monomer Xa having no hydroxyl group and an ethylenically unsaturated monomer Xb having a hydroxyl group or a carboxyl group, and has a weight average molecular weight of 500-100,000.