A first decoration, probably painted shortly after the construction of the church was constituted by a painting with a dark blue base, that is still partially preserved on the back wall and on the vaults, where two tondi with Christ in Glory and the Agnus Dei were made.

Around 1390, unknown artists, known as the “masters of the Oliveri chapel” painted the main cycle of frescos. The first artist, maybe the oldest one, is more traditional and seems to be linked to the Tuscan artistic environment, that during the period extended its influence in Liguria.

The second painter, with more modern ways and probably younger, seems more taken with colour, and used varied and luminous tonalities for the rendering of the figures.

On the back wall of the chapel, on the sides of the tall window, the Eternal Father with angels to his left was represented and below there were the scenes that represented the Annunciation, Meeting at the golden gate, Prayer in the Garden but only the face of Christ remains.

In the lower part a devotional fresco with Saint Catherine, abbot Saint Bernard and another martyr Saint was painted by a third painter.

On the left side the Stories of the life of Mary include, from the bottom towards the top, the naming of St. John the Baptist, the marriage of the Virgin, the escape from Egypt, the dispute in the temple, the death of the Virgin and in the lunettes the apparition of the Assunta to St. Thomas with the miracle of the belt and lastly the coronation of the Virgin, both with signing angels.

The scenes from the Passion of Christ, on the right wall, very tampered with due to the opening of a few windows during the prison phase, consist instead of a Crucifixion on the back wall of the pointed-arch sepulchre that is decorated with tondi with busts of the evangelists and saints.

The superior paintings present only a few pictorial fragments with a Pity scene, of which remain only the traces of a figure of a saint that presents the kneeling family of the commissioner, the discovery of the empty tomb on behalf of the Maries and in the lunette a Resurrection or the ascension of Jesus.

The chapel, originally belonged to the Oliveri family, whose crest was painted on the vaults. Before 1589 it passed on to the Arnaldi family and the area went through various transformations linked to the different tastes in style; in this phase the frescos were tapped and covered with stucco. After 1865, the chapel was adapted to the necessities of the prison and with that new openings and spatial divisions were made.

The cycle of frescos, discovered in 1965 under the various layers of plaster, went through a complex restoration in 2003. In this occasion the paintings, that had been removed in 1865 when the monastery was suppressed by the Accademia Ligustica di Belle Arti and the paintings were taken to Genoa, were repositioned in their original settings.