The performance of historical masonry is highly influential on the seismic vulnerability of ancient buildings. This chapter presents the characterization of traditional tuff masonry in an aristocratic Villa in Naples. Comparing the values of material properties obtained from diagnostic investigations with those indicated for the corresponding masonry typologies in the Italian Code, a better grade has resulted for the masonry of the villa, which appeared constructed with particular care and quality. Additional variability in the behaviour of tuff masonry derives from the quality of the mortar, usually pozzolanic, and the construction modality and details. The diagnostic campaign was organised taking into account the particular situation of the Villa that is listed as cultural heritage building, implying a non-destructive and noninvasive approach. The vaulted system of the basement presented difficult conditions for the application of thermographic tests and for a more detailed investigation on their building techniques.