In December 2019 the canonical recognition and the multidisciplinary study of the human remains of sant’Atto da Pistoia († 1153) took place in the cathedral of San Zeno in Pistoia. The investigation, which continued in the following months, included the anthropological and paleopathological examination, the radiological study through conventional X-ray and Computed Tomography, histological and immunohistochemistry analyses, radiometric dating and isotopical study for the reconstruction of the nutritional model and of the place of provenance. The results of the study showed that sant’Atto was a naturally mummified ancient human body. The state of preservation is good, even if evidences of restorations appeared in some areas of the body. Reconstruction of the biological profile of Atto outlines a male individual aged over 50 years, with a stature of about 168-170 cm. Paleopathological investigation indicated that the saint was suffering from caries, pulmonary anthracosis and osteoarthritis. The histological analysis showed a very good state of preservation of biological tissues. Radiocarbon dating places the saint's death between the tenth and eleventh centuries. The nutritional profile indicates a diet based on terrestrial and marine proteins, compatible with the status of abbot and bishop. Isotopical study suggests a compatibility of provenance of the saint with some Italian geographical areas, including the Alpine area, Tuscany, Lazio or Calabria.