A gas sensor element includes: an element main body including an oxygen concentration detection cell and an oxygen pump cell; and a protective layer that covers the element main body. The element main body includes a heater section. The heater section is a heating element that heats the oxygen concentration detection cell and the oxygen pump cell. The protective layer includes: a first protective layer including a carrier composed mainly of a white ceramic and a noble metal catalyst supported on the carrier; and a second protective layer that is a layer composed mainly of a white ceramic and supporting no noble metal catalyst. The second protective layer externally covers the first protective layer, and a surface of the second protective layer serves as the outermost surface of the protective layer. The thickness of the second protective layer is smaller than the thickness of the first protective layer.