The present invention relates to a gas barrier film for a paper or paperboard based packaging material, said gas barrier film comprising: a microfibrillated cellulose layer (MFC layer), at least one surface of which has been metallized; and a polymer dispersion coating layer disposed on at least one surface of the MFC layer. The present invention further relates to a paper or paperboard based packaging material, containers and carton blanks comprising the gas barrier film, and to a method for manufacturing the gas barrier film.