Archaeological research began at Dos del Castel di Teglio (SO) in 2021 with non-invasive investigations, and continued in 2022-2023 with excavations. The site, already known to present occupation evidence dating from pre/proto-history to the medieval period, was initially investigated with a series of trial trenches in order to evaluate its archaeological potential, and then open-area excavations took place, in particular in the area south of the castle’s tower. Here, numerous structures from various medieval occupation phases were identified. The first, dating to the 9th -12th century, was represented by faint traces of structures, probably made of perishable materials, around the tower. In a second phase, between the mid-13th and early 14th century, these structures were replaced by a series of buildings, partly residential, with stone and lime mortar walls. This busy period of construction inside the castle probably relates to the armed clashes that characterized the Valtellina at this time. The structures were probably built to house the castle’s military garrisons. They remained in use, with slight modifications, throughout the 15th century until the site was abandoned, probably during the course of the 16th century. The site’s military nature is supported by the finds recovered during the excavation, in particular of the beaten-earth floor surfaces. In fact, numerous iron objects relating to weapons (arrowheads, crossbow bolts, knives) and armour (chainmail, elements from plated body armour) were recovered.