A prismatic multilayer gas sensor element and method of making the same, the prismatic multilayer gas sensor element (1) having a substantially rectangular cross section, and including a gas-sensing cell portion (2) formed at a distal end portion of the prismatic gas sensor element (1); and a posterior lead portion (3) adjoining the gas-sensing cell portion (2). The longitudinal lateral surfaces of the posterior lead portion (3) are coated with a non-porous alumina layer (11), the non-porous alumina layer (11) having a multilayered structure including at least a joining layer (11a) and a surface layer (11b). The longitudinal lateral surface of the gas-sensing portion (2) is not coated with a non-porous alumina layer.