[1] Though Petronilla was originally venerated as the daughter of Peter, more recent study has shown that she belonged to the Roman family of the Aurelli.

Stories associated with her include those that relate that she was so beautiful that Peter had locked her up in a tower to keep her from eligible men; that a pagan king named Flaccus, wishing to marry her, led Petronilla to go on a hunger strike, from which she died.

[1] After the erection of the basilica over her remains and those of Nereus and Achilleus in the 4th century, her cult extended widely and her name was therefore admitted later into the martyrology.

[8] Almost all the 6th- and 7th-century lists of the tombs of the most highly venerated Roman martyrs mention Petronilla's grave as situated in the Via Ardeatina near Nereus and Achilleus.

[10] This church, built into the above-mentioned catacomb, has been discovered, and the memorials found in it removed all doubt that the tombs of the three saints were once venerated there.

[11] A painting, in which Petronilla is represented as receiving a deceased person (named Veneranda) into heaven, was discovered on the closing stone of a tomb in an underground crypt behind the apse of the basilica.

It is thus clearly established that Petronilla was venerated at Rome as a martyr in the 4th century, and the testimony must be accepted as certainly historical, notwithstanding the later legend which recognizes her only as a virgin (see below).

Another known, but unfortunately no longer extant, memorial was the marble sarcophagus which contained her remains, under Pope Paul I translated to St. Peter's Basilica.

The sarcophagus was discovered, in the very chapel dedicated to her in Old St Peter's, under Pope Sixtus IV, who hastened to inform Louis XI of France.

[8] In 757 the coffin containing the mortal remains of Petronilla was transferred to an old circular building (the mausoleum of Emperor Honorius[14][15] dating from the end of the 4th century) near Old St Peter's.

When St Peter's was rebuilt in the 16th century, the old chapel and former mausoleum was demolished[14][17] and Petronilla's relics were translated to an altar dedicated to her in the upper end of the right side-aisle of the new basilica (near the cupola).

The Healing of St Petronilla is the name of a tapestry made for Guillaume de Hellande, Bishop of Beauvais, in the 15th century.