Mary, Queen of the World Cathedral

A small chapel is dedicated to baptism ceremonies. The marble baptismal font is mounted on a stucco crucifix sculpted by Louis-Philippe Hébert.

The bishop's mortuary chapel is located on the east wall of the cathedral.

The burial chapel, completed in 1933, is located on the east wall of the building, east of the nave, halfway between the main entrance and the altar in the centre. The tomb of Mgr. Bourget, an art work which was created in Rome, is located in the centre. The remains of the bishop that lay in a crypt under one of the pillars in the cathedral were transferred to his tomb on April 27, 1933. The titular bishops are buried on the west side and the auxiliary bishops on the east-hand side.

The walls and floors are made of marble imported from Italy and feature several mosaics. The bronze plaque above the altar depicts St. Peter's Basilica in Rome.

Since the cathedral was running out of space for burying auxiliary bishops, a second chapel was built next to the original one in 2005. Here an additional 15 vaults have been prepared.

This chapel, also known as the Marriage Chapel, is located on the west side of the nave (across from the Bishop's Chapel). This work of art features a wood-carved altarpiece, decorated with gold leaf and framing a painting depicting the Assumption of the Virgin Mary. It was made around 1635 at the Benedictine Abbey in Bellelay, Switzerland by a Spanish monk. When the monks were forced to leave during the religious retaliation, the occupying French troops sold all the precious furniture in the Abbey. At the beginning of the 20th century, the Austrian architect-conservator Rodolphe Messmer discovered the altarpiece in the church of Suarce, France and acquired it. In 1994, Bruno Messmer donated it to the Roman Catholic Archdiocese of Montreal.

In 1957, Cardinal Paul-Émile Léger put the chapel at the disposal of the Order of Malta. The stained-glass windows are dedicated to this Order.

A neo-baroque ciborium is located under the dome of the building

Covering the altar, which is located under the dome, is a neo-baroque ciborium or baldaquin, with twisting columns. It was created in Rome in 1900 by Joseph-Arthur Vincent and is a reproduction of the famous 'baldacchino' in St. Peter's Basilica, created by Gian Lorenzo Bernini.

It is fully hand-made and made with red copper and gold leaf. The angels, garlands and papal insignia were sculpted between 1910 and 1911 by Olindo Gratton. This work of art was a donation to the cathedral by the Sulpicians.

Built by Casavant Frères, the organ was inaugurated on September 22, 1893. At that time, it consisted of 56 stops on three manuals and a pedal board. In 1951 the organ required maintenance, after which it was decided to rebuild the entire organ. Again, Casavant Frères was chosen for the job, and they added 20 stops and a manual.

In 1995–1996, the instrument was restored by Guilbault-Thérien from Saint-Hyacinthe. A few more additions were made, so that now the organ counts a total of 93 stops, four manuals and one pedal board.

A paintings of the first Mass celebrated at Rivière-des-Prairies by Fr. Denis Jamet. The painting is one of several located inside the cathedral.

The aisles of the nave and the arches in the transept contain painting depicting historical events in the early days of Montreal (called Ville-Marie at the time). It contains nine paintings and still three empty spaces. The paintings are:

1. The aforementioned painting of colonel Athanase de Charette, commander of the Papal Zouaves of Montreal. Work by Lionel Ryder.
2. Marguerite d'Youville singing "Te Deum" to children during the fire that destroyed her hospital on May 18, 1765. Work by Georges Delfosse.
3. Marguerite Bourgeoys teaching her Amerindian pupils in 1694 at the foot of one of the historic towers on ground belonging to the Sulpicians. Work by Georges Delfosse.
4. The martyrdom of Jean de Brébeuf and Gabriel Lalemant in the land of the Hurons. The Iroquois tortured the Jesuit missionaries, of whom de Brébeuf can be seen in the centre with his hands tied to a stake. Work by Georges Delfosse.
5. Father Barthélemy Vimont saying the first Mass in Montreal on May 18, 1642. Paul de Chomedey, Sieur de Maisonneuve and Jeanne Mance, the co-founders of Montreal, can be seen attending the Mass. This work by Ernest Laurent was a gift from the French government to Paul Bruchési.
6. The consecration of the Associates of Montreal's project. On February 3, 1641, noble man and women, and priests, who dreamed of founding the city of Ville-Marie in New France, attend a Mass celebrated by Jean-Jacques Olier in the Notre-Dame of Paris to pray for the protection of Our Lady for what many considered to be a "foolish undertaking." Work by Georges Delfosse.
7. The first Mass celebrated at Rivière-des-Prairies by Father Denis Jamet on June 24, 1615. Joseph Le Caron holds the edge of Jamay's chasuble. Samuel de Champlain, founder of Quebec City, is in the centre. Work by Georges Delfosse.
8. The martyrdom of Nicolas Viel (seen in the boat) and his disciple Ahuntsic (seen already fallen in the water) by three Amerindians on the rapids at the Sault-au-Récollet. Work by Georges Delfosse.
9. Jeanne Mance, co-founder of Montreal, and the nursing sisters of Religious Hospitallers of St. Joseph tend to a sick child Montreal's first hospital, Hôtel-Dieu de Montréal. Work by Georges Delfosse.

In the apse is a statue of Mary, Queen of the World, patron of the cathedral, by Sylvia Daoust. Statues of the 12 apostles on the façade of St. Peter's, the front of the cathedral is topped by statues of the patron saints of 13 parishes of Montreal who donated them, including St. John the Baptist and St. Patrick. All of the statues were sculpted by Olindo Gratton between 1892 and 1898. Saints with statues atop the main entrance of the cathedral include:

Statues of the patron saints of the parishes of Montreal atop the cathedral's main entrance

Next to the church, there's also a monument for Ignace Bourget.

Several texts in golden letters decorate the inside of the cathedral. Since the building was originally dedicated to Saint James the Greater (and it still is), it explains why most of the Latin texts refer to his life.

Texts in the nave include:

Golden letters adorn the inside of the cathedral

• On the side of the cathedra (east side): "He [James] is one of the three Apostles whom the Savior loves the most. In Judea and Samaria he converts many to the Christian faith." (Latin: "Is unus fuit ex tribus Apostolis, quos Salvator maxime dilexit. In Judæa et Samaria, plurimos ad Christianam fidem perduxit.")
• On the side of the tabernacle (west side): "He also converts some people in Spain, in Jerusalem he is condemned to death. He is the first of the Apostles that bears witness to Jesus with his blood." (Latin: "In Hispania aliquos convertit, Jerosolymae capite damnatus est. Primus apostolorum profuso sanguine testimonium Jesu dedit.")

The texts featured in the transepts are based on Matthew 20:22–23 and the brothers James and John asking Jesus to sit besides him, one on his left and one on his right, in his Kingdom.

• On the side of the cathedra (east side): "And Jesus, answering, said: You know not what you ask. Can you drink the chalice that I shall drink? They said to Him: We can. And he told them:" (Latin: "Respondens autem Iesus dixit nescitis quid petatis potestis bibere calicem quem ego bibiturus? Sum dicunt: Ei possumus. Ait illis:")
• On the side of the tabernacle (west side): "My chalice indeed you shall drink, but to sit at my right or left is not for me to grant, [these places] belong to those for whom they have been prepared by my Father." (Latin: "Calicem quidem meum bibetis sedere autem ad dexteram meam et sinistram non est meum dare vobis sed quibus paratum est a Patre meo.")

Two other texts, both based Matthew 16:17–19, speak of the vocation of Saint Peter, head of the Apostles. These texts can also be found in the nave inside the St. Peter's Basilica in Vatican City.

The cupola of the cathedral, which features text inside of it.

• Inside the cupola: "You are Peter and upon this rock I will build my Church. And the gates of hell shall not prevail against it. And I will give you the keys of the Kingdom of Heaven. (Latin: "Tu es Petrus, et super hanc petram aedificabo Ecclesiam meam, et portae inferi non praevalebunt adversus eam. Et tibi dabo claves Regni coelorum")
• In the chancel and apse: "And whatsoever you shall bind upon earth, it shall be bound also in Heaven: And whatsoever you shall loose on earth, it shall be loosed also in Heaven. Feed my sheep." (Latin: "Quodcumque ligaveris super terram, erit ligatum etin coelis: et quodcumque solveris super terram, erit solutum et in coelis.")
• At the base of the cupola: This text is fragmented into four physical sections. It is based on Revelation 4:8 from the Apocalypse and dedicated to the glory of God: "Holy, Holy, Holy, the Lord, who is, who was, and who is to come." (Latin: "Sanctus sanctus sanctus Dominus qui erat qui est qui venturus est.")