Historically, the Catholic religion played a very important part in politics and law. Before changes were made to the Constitution in 1994, the two top leaders of Argentina had to be Roman Catholic. Today, although officially 90% of Argentinians are Roman Catholic, fewer than 20% attend hurch regularly. Most go for weddings, funerals and major feast days.

Many Argentinians make annual pilgrimages to holy sites and local shrines. The most popular place is Luján, 65 km west of Buenos Aires. Each year, thousands of people make the pilgrimage on foot from Buenos Aires to honour the Patron Saint of Argentina, the Virgin of Luján. According to tradition, in 1620 a statue of the Virgin was being carried from town to town in a cart. The cart got stuck at Luján, Buenos Aires Province, and could not be moved. The people built a chapel for the Virgin to protect the statue. Today there is a large basilica where the chapel once stood.

Most provinces and cities have a patron saint. In the northern Salta province, people make pilgrimages to honour "Our Lord of the Miracles" on September 15. In 1592, a statue of Jesus Christ was washed up out of sea and was carried inland to the Salta City. This statue, the people of Salta believe, has saved them from earthquakes and other dangers. During the fiesta, people parade through the streets of Salta City carrying the statue of Jesus Christ.

Another important pilgrimage site is Itatí, in Corrientes Province on the Parana River, where people honour the Virgin of Itatí every July 16. The statue of the Virgin was carved by a Guaraní artist.

Although the Constitution states that the federal government is Roman Catholic, it also guarantees freedom of religion for all. Argentina has many Jews and Muslims, as well as members of Russian, Greek and Syrian Orthodox churches and Protestant denominations.

Some indigenous people follow the customs of the Catholic Church, others have kept their traditional beliefs. Many of the Colla people in the northwestern provinces of Salta and Jujuy attend Catholic churches and also follow traditional forms of worship. In Catamarca province, there is an annual festival to honour Pachamama, who represents mother earth.