Second ecumenical council, an effort to attain consensus in the church through an assembly representing all of Christendom, except for the Western Church, confirmed the Nicene Creed, expanding the doctrine thereof to produce the Niceno-Constantinopolitan Creed, and dealt with sundry other matters. It met from May to July 381 in the Church of Hagia Irene and was affirmed as ecumenical in 451 at the Council of Chalcedon.

Seven canons, four of these doctrinal canons and three disciplinary canons, are attributed to the council and accepted by both the Eastern Orthodox Church and the Oriental Orthodox Churches; the Roman Catholic Church accepts only the first four because only the first four appear in the oldest copies and there is evidence that the last three were later additions.

• The first canon is an important dogmatic condemnation of all shades of Arianism, and also of Macedonianism and Apollinarianism.
• The second canon renewed the Nicene legislation imposing upon the bishops the observance of diocesan and patriarchal limits.
• The third canon reads:
  The Bishop of Constantinople, however, shall have the prerogative of honor after the Bishop of Rome because Constantinople is New Rome.*
• The fourth canon decreed the consecration of Maximus as Bishop of Constantinople to be invalid, declaring "that [Maximus] neither was nor is a bishop, nor are they who have been ordained by him in any rank of the clergy". This canon was directed not only against Maximus, but also against the Egyptian bishops who had conspired to consecrate him clandestinely at Constantinople, and against any subordinate ecclesiastics that he might have ordained in Egypt.
• The fifth canon might actually have been passed the next year, 382, and is in regard to a Tome of the Western bishops, perhaps that of Pope Damasus I.
• The sixth canon might belong to the year 382 as well and was subsequently passed at the Quinisext Council as canon 95. It limits the ability to accuse bishops of wrongdoing.
• The seventh canon regards procedures for receiving certain heretics into the church.

The third canon was a first step in the rising importance of the new imperial capital, just fifty years old, and was notable in that it demoted the patriarchs of Antioch and Alexandria. Jerusalem, as the site of the first church, retained its place of honor.