The sacristy is a rectangular room which is accessed through a narrow transverse rectangular antechamber. This was built under the direction of Carlo Murena in the 18th century restoration. The sacristy is in late Baroque style in white and puce with Corinthian pilasters supporting an entablature. The corners are slightly chamfered, and in them are four slightly elliptical tondi containing paintings representing the four Latin Doctors of the Church (Sts Ambrose, Augustine, Leo and Jerome). The altarpiece, by Gianfranco Romanelli, depicts St Thomas of Villanova Giving Alms (ca. 1660).