Values for δ13C and δ18O obtained from molar samples from three individuals pertaining to Glyptotherium sp. from Cedral (San Luis Potosí, México) are provided and are utilized to infer general aspects of glyptodont diet and habitat. On average this animal showed a C3/C4 mixed diet, with a high consumption of C4 plants. Comparisons of the δ13CVPDB and δ18OVPDB values for glyptodonts with horses, mastodons, mammoths and tapirs from the same locality show that glyptodonts from Cedral lived in an open habitat.