1. Construction. The sacristy, built before 1616, is similar to the one inside of  “il Gesù”. The motifs of the central panel in the ceiling and the lunettes that conclude the opening of the windows are recurrent in both sacristy. The travertine marble twin doors in the entrance corridor and the inscriptions on them, preceded by the death of Alessandro Peretti Montalto (1623), confirm that the building of the sacristy was before 1616 and therefore not attributable to Paolo Maruscelli (1594-1649) , But to Gerolamo Rainaldi (1600-1620). “For his majestic architecture, for amplitude and comfort, Pius IX  said it was the best sacristy in Rome.”

2. Walnut-tree cabinets. The light, that kindly falls by a double sequence from the windows, exalts the original color of the large magnificent eight closets of the seventeenth century, all made with solid wood of walnut-tree. A wise work of sculpture, which the anonymous artist has enriched with fluted pilasters and corinthian capitals, on which an entablature runs, surmounted by frames.

3. The paintings. In the sacristy there are interesting paintings painted on canvas, among which: 4 paintings by popes: Paul IV (1555-59), founder of the Theatine order; Urban VIII (1623-1644), to whom the Order owes the beatification of the St. Andrew Avellino (1624) and st. Cajetan (1629); Clement X (1670-1676), to whom the general father was very grateful because of the Canonization of st. Cajetan (1671); And Clement XI (1700-1721), flanked by the two theatine cardinals: Pignatelli and Tomasi, also thanked by the General Father of the Order for the canonization of st. Andrew Avellino (1712).

On the back wall stands out the beautiful canvas of the Crucifix with the Virgin and st. John(4.65 x 2.60 m.) By Giovanni De’Vecchi. Above the front door, a portrayal of Alessandro Peretti with Maderno and his project for the facade. Other paintings, rounded and octagons, all perhaps from the shop of Giacinto Brandi, except those ones which depicting episodes of the life of st. Cajetan for by Andrea Sacchi. It is also a must-see “Crist in front of Caiaphas” by the School of Gherardo delle Notti ..