The funerary chapel of Cardinal Basilios Bessarion is behind the Odescalchi Chapel, the building of which left it walled off and inaccessible until 2005. The tomb of Cardinal Bessarion was removed from the church, in 1702, to the cloisters of the adjoining convent.

The chapel was completed and the frescoes were executed by Antoniazzo Romano in 1483, but was apparently derelict and its frescoes whitewashed when the Odescalchi Chapel was built within it. Rather than demolishing the existing structure, the builders of the latter simply constructed it within the older chapel's walls and so left a very tight space between the new walls and the old. Remarkably, the arrangement was then completely forgotten about until restoration work on the adjacent Palazzo Colonna in 1959.

Top Register
The upper section of the frescoes consists of a Host of Angels adoring Christ in Majesty; unfortunately, only the lower edge of Christ's robe survives.

Middle Register
The middle section of the frescoes shows two scenes from stories of legendary apparitions of St Michael. The left hand one concerns the foundation legend of the shrine at Monte Gargano, whereby the saint appeared in 490 to the Bishop of Siponto (the city appears in the fresco) to ask that the shrine be founded in a cave on the mountain. The depiction here shows the saint appearing as a bull in the sacred cave, with archers shooting at it only to have their arrows bounce off.

The right hand scene concerns the Apparition of St Michael to St Aubert of Avranches, bishop of that city in France in the 8th century. This allegedly led him to found the famous shrine and monastery on the island of Mont Saint Michel, shown in the background. The figures in the fresco are standing on a beach, and include Basilian monks and Franciscan friars (Bessarion was one of the former). To the left of richly dressed saintly archbishop are two figures, one in purple with part of his face missing and one in vermillion. These are cardinals of the della Rovere family; the former is the future Pope Julius II, and the latter the future Pope Sixtus IV.

Lower Register
The middle of the lower register was the original location of Romano's icon of the Madonna and Child that is now on the altar in the Chapel of St Bonaventure; it has been replaced here with a copy. To either side of this are two mediocre portraits of St Eugenia and St Claudia.