The Sacristy built in the bishopric of D. Fr. Gonçalo de Morais from 1603-1617, has a vault with a broken cradle, based on strong torso arches and granite consoles embedded in the wall. It underwent works of increase in the beginning of the century. XVIII, being completed in 1701. This sacristy was gilded and painted by Manuel Leão and Mateus Nunes de Oliveira. This sacristy would be reformed with his "brutesco" paintings that Nicolau Nasoni found when he arrived in Porto in 1725, to paint the interior of the Cathedral, paintings that disappeared in the fire of 1731, and which led Nasoni to be in charge from that date of the decoration of this Sacristy.

From its side walls, which show frescoes by Nicolau Nasoni, ten framed paintings are suspended: two of them are on canvas, with the themes The Wedding of Canaã and the Wedding of the Virgin, and were executed in 1734 by the Florentine painter Carlo Antonio Leoni. The remaining eight, on wood, come from a retable structure, probably from the previous main altarpiece and were attributed to Francisco Correia. Assuming that the eight panels were part of the dismantled main altarpiece, ordered by Bishop D. Gonçalo de Morais in 1606, these would have been carried out between 1606 and 1610, the year in which the altarpiece was finished. The record is from 1610 and portrays some of the episodes of the Childhood of Jesus: Annunciation, Visitation, Adoration of the Shepherds, Adoration of the Magi, Circumcision, Presentation of the Child Jesus in the Temple, The return of the Holy Family from Egypt and The Child Jesus among the Doctors. The reuse of the panels meant that, due to their weak state of conservation, they were intervened in 1727. The person responsible for this intervention was the Italian João Baptista Pachini who altered the panels in such a way, that little remains of the original painting from the 17th century.