The Chaldean Catholic Church, which today constitutes the largest Church in Iraq, is the body which has resulted from some parts of the Ch. of E. coming into communion with the see of Rome since the 15th cent. The first such union was in Cyprus as early as 1445, but the Church now traces its patriarchal line to the consecration of Yoḥannan Sullaqa as ‘Patriarch of Babylon’ in 1553. Relations between his successors and Rome became attenuated, and a second patriarchal line came into being at Amid (Diyarbakır) in 1681. (The second patriarch in this line, Yawsep II, was an important literary figure.) The Diyarbakır patriarchate came to an end in 1828, and the Metropolitan of Mosul, Yoḥannan Hormez, was confirmed as patr. in 1830. The line of patriarchs has been continuous from his time until the present, although the patriarchate was moved from Mosul to Baghdad in 1950.

The present patr., since 2003, is His Beatitude Mar Emmanuel III Delly Chaldean Patriarch of Babylon. (This is his full style. Mar Emmanuel was also made a Cardinal in 2007.) His see is in Baghdad. Also In Iraq, outside Baghdad, there are archdioceses of Arbela, Baṣra, Kirkuk, and Mosul, and dioceses of Alqosh, Amadiyya, ʿAqra, Sulaymaniyya (Duhok), and Zakho; in Iran: Ahwaz, Salmas and Urmia, and Tehran; Syria: Aleppo; Lebanon: Beirut; Turkey: Istanbul (titular of Diyarbakır); Egypt: Cairo; United States: Southfield, MI and San Diego, CA. Since 1990 all the Eastern Catholic Churches have had their own Code of Canon Law. In 1990 Babel College, for higher theological and philosophical studies, was established in Baghdad, with Y. Habbi as its President (1991–2000); in 2006, however, owing to the dangerous situation in Baghdad, Babel College had to be transferred to ʿAynkawa (near Arbil). In recent decades, as a result of the Iraq-Iran War, the sanctions after the Iraqi invasion of Kuwait, and the lack of security that has resulted from the American and British invasion in 2003, large numbers have left Iraq and there are now many more Chaldeans living either as refugees in Syria and Lebanon, or as immigrants in the diaspora (above all in North America), than remain in Iraq.