This paper aims at describing the use of the prepositional accusative in Medieval Sardinian in order to outline the typology of this feature and to determine its stage of grammaticalization. In particular, I analyzed the data emerging from the so-called Codaghe di San Pietro di Silchi, a monastic register which belongs to the Ancient Logudorese ‘scripta’. To reach this aim, I took into account both the functional and formal dimension of analysis in a typological framework. The data, obtained by quantifying all the occurrences of the different uses of the prepositional accusative in the above mentioned text, show both some unexpected and expected results.