Agnes was the sister of St. Clare and her first follower. When Agnes left home two weeks after Clare’s departure, their family attempted to bring Agnes back by force. They tried to drag her out of the monastery, but all of a sudden her body became so heavy that several knights could not budge it. Her uncle Monaldo tried to strike her but was temporarily paralyzed. The knights then left Agnes and Clare in peace.

Agnes matched her sister in devotion to prayer and in willingness to endure the strict penances which characterized their lives at San Damiano. In 1221 a group of Benedictine nuns in Monticelli (near Florence) asked to become Poor Clares. St. Clare sent Agnes to become abbess of that monastery. Agnes soon wrote a rather sad letter about how much she missed Clare and the other nuns at San Damiano. After establishing other Poor Clare monasteries in northern Italy, Agnes was recalled to San Damiano in 1253 when Clare was dying.

Agnes followed Clare in death three months later. Agnes was canonized in 1753.