A packaging material for electrochemical cells, which has insulating properties sufficient for preventing a short circuit, while exhibiting excellent electrolyte solution resistance and water vapor barrier properties. A packaging material for electrochemical cells is obtained by sequentially laminating a metal layer, an adhesive resin layer and a thermally adhesive resin layer in this order, wherein: a base coating layer is provided between the metal layer and the adhesive resin layer; and the base coating layer contains at least a zirconium oxide (A) having an average particle diameter within the range of from 1 nm to 500 nm (inclusive), one or more phosphorus-containing compounds (B) selected from the group of phosphorus compounds having 4 or more phosphonic groups in each molecule, and an acid-modified polyolefin resin (C).