The vestible of the sacristy has an altar under its lunette window, and is hence a chapel dedicated to the Immaculate Conception of Our Lady. It is the Cappella Capranica. The artworks are by Pier Francesco Mola.

Memorials in here are to Giovanni Luigi Priolo, a Venetian patrician (d.1801) to the left, and Gabrielle Scaglia, Countess of Saluzzo (d. 1796) to the right.