What is the Chaldean Church? Are They Catholics?

The Chaldean Catholics are indeed Catholic! They originated in the Nestorian heresy, but parts of them were reconciled with Rome in 1552. They form one of the 23 Eastern Churches subject to the Pope.

From Aleteia

By Matthew Grenn

When we hear news about Christians in the Middle East, there are often references to the Chaldeans or the Chaldean Church. Who or what are they?

The Chaldean Catholic Church is often mentioned in news reports about the Christians who live in countries such as Iraq, Iran, and Lebanon, where its members have a historical presence. It’s also present in other parts of the world where Chaldean Catholics have emigrated and made their homes. Consequently, during these days when there is conflict in the Middle East, it’s helpful to understand who Chaldean Catholics are.

Churches within the Church

First, it’s important to remember that while there is only one Catholic Church, there are groups within it who are united by particular regional, ethnic, historical, liturgical, and theological bonds. In some cases they are officially referred to as Churches (with a capital C) without detriment to the unity of the whole Catholic Church.

These Churches have a long history. The New Testament often refers to “the Church in …” one city or region or another, such as the Church in Corinth or the Church in Rome. Over time, due to many factors (geographical, political, etc.), there evolved distinct theological and liturgical traditions (keep in mind these Churches didn't have the internet to stay in touch, so it was natural that within the limits and great time-delays in communication, differences would arise). Some share the same liturgy, or rite, but are differentiated by other historic or national elements.

Twenty-four of these traditions are formally recognized within the Catholic Church today. To give a few examples, there are the Maronite Catholic Church (rooted in Lebanon), the Syro-Malabar Catholic Church (rooted in India), the Ethiopian Catholic Church (no explanation needed), and of course the Chaldean Catholic Church.

The origin of the Chaldean Catholic Church

In the 5th century, the Christians who lived in the Sasanian Empire (roughly modern-day Iraq and Iran) embraced Nestorianism. This was a Christological heresy that held that Christ the man and God the Son were two distinct persons, not essentially united, thus denying the Incarnation.

This implied a break with the rest of Christianity. Some sources suggest that this may have been intentional: a way for Persian Christians to separate themselves from perceived foreign influence, and free themselves from persecution by the Sasanian government. (This situation of Christians in what is now Iran, being persecuted because they are perceived as foreign agents of some sort, is sadly familiar; it remains a challenge for Christians in Iran today.) This group became known as the Church of the East.

The Church of the East actively evangelized and spread to India, China and Mongolia. However, most of the Nestorian communities outside of Persia were wiped out by the Mongol leader Timur in the 14th century. Starting in 1551, large groups of the remaining Nestorians started to reunite with Rome.

The region where the Church of the East had been founded was known before the Sasanian Empire as Chaldea, mentioned often in the Bible. Consequently, the Nestorians in that region who reunited with the Church of Rome were called Chaldean Catholics. 

In fact, their Chaldean identity remains important today. In a recent letter, Cardinal Louis Raphael Sako, Chaldean Patriarch of Baghdad (who retired in early March, 2026), wrote, “We are Chaldeans, our identity is Chaldean, our nationality is Chaldean, and our Church is Chaldean Catholic.”

Where do Chaldean Catholics live today?

The Patriarch of the Chaldean Catholic Church has his episcopal see in Baghdad, Iraq, in the Church’s land of origin. Chaldean Catholics are in fact the largest Christian population in the country, although still a tiny minority overall. While it’s difficult to get exact numbers, and ongoing conflicts can cause major shifts due to forced migration, recent estimates say there are about 250,000 Chaldean faithful there. 

There are also 20,000-30,000 in Lebanon, and other Chaldean Catholic communities spread through the Middle East, most of which are difficult to measure due to their status as an often-persecuted minority.

Chaldean Catholics have migrated, whether to flee conflict or to seek better opportunities, throughout the world. The largest Chaldean Catholic population outside of the Middle East is actually found in the USA, in the state of Michigan.