Anthony Kauleas was born around 829 to a Greek-Phrygian Byzantine family that moved to Constantinople during his childhood. He entered monastic life at age 12 at the monastery of Kauleas in Constantinople (from which he took his surname Kauleas), becoming abbot of the monastery in his adult years.
On August 12, 893, after the death of Patriarch Stephen I (the son of Emperor Basil I the Macedonian), Anthony was elected Patriarch of Constantinople by Emperor Leo VI the Wise — selected for his reputation of holy ascetic life and pastoral moderation, after the decades of Ignatian-Photian controversy that had divided the Constantinopolitan Catholic-Christian community.
His eight-year patriarchate (893–901) was devoted to the reconciliation of the Ignatian (anti-Photian) and Photian (moderate-conciliarist) parties — producing the peace synod of 899 that formally ratified the mutual reconciliation of the two parties under the shared patriarchal authority.
He maintained cordial relations with Pope Stephen V and Pope Formosus in Rome — preserving the continuing Catholic-Orthodox communion that the John VIII / Photios reconciliation of 879 had restored.
Anthony died at Constantinople on February 12, 901 — having restored the internal peace of the Constantinopolitan Catholic Church after the decades of Ignatian-Photian division. His successor Nicholas I Mystikos would face the new crisis of Emperor Leo VI's fourth-marriage controversy.