Situated on the left bank of the Sabato river, the city of Abellinum (Campania region, southern Italy) represents a tangible testimony to the influence of the Roman civilization in Irpinia. At the site, where the remains of the public area of the town are preserved, archaeological excavations nearthed a monumental Pompeian domus, likely owned by Marcus Vipsanius Primigenius, a freedman of Agrippa, son-in-law of Augustus. The rooms preserved fine wall paintings of 3rd and 4th Pompeian style, reflecting the social status of the owner. From four rooms overlooking the peristyle, eight specimens of decorated plasters were collected, and petrographic and spectroscopic analyses were carried out to investigate the plastering and painting technology. Thin sections of all plasters depicted a multilayer technology, although differences in mix designs of the supports were highlighted. Some samples are pozzolanic plasters, containing volcanic aggregate, others can be classified as cocciopesto because of the presence of ceramic fragments mixed to the volcanic aggregate. Finally, the presence of marble powder also permitted the identification of marmorino. Moreover, the pigments, applied using a fresco or lime-painting techniques, consist of pure or mixed Fe- and Cu-based pigments to obtain yellow, orange, red, pink, and blue decorations.