Since it is a building imbued by Gothic style, its interior is entirely decorated, full of religious symbols and beautifully ornamented with stained glass windows, as well as pictorial works.

Light green and blue shades are prominent inside, and, structurally speaking, every existing arch is ogival, thereby representing the style adopted, as well as the ceilings of the three naves comprising the temple. They are profusely decorated with a wide variety of motifs and painted in golden shades. Ribbed vault ribs stand out due to the symbolic, geometric and vegetal motifs used in their decoration. It is certainly interesting to note that all columns and pillars are decorated with serpentine motifs, very influenced by the development of Solomonic column from the Baroque period, covered with strips in contrasting colors and from where flower bouquets sprout, complementing decoration. The play of colors is usually complementary, green and red for a better contrast, and a golden line bordering the set for an increased emphasis.

Lateral walls, painted in cobalt blue, are decorated with small golden fleurs-de-lis, a symbol of power.

Central nave is crowned with a beautiful ribbed vault ceiling, entirely decorated with different golden filigrees, serpentines and garland emphasizing the geometry of the lockets painted by Italian artist Pedro Pelli about Biblical figures. From the intersection of ribs in the central part, pretty French crystal lamps hang. Curiously, they are one of the few exceptions having color glass beads that are completely restored.

In the upper part of the nave there are stained glass windows produced by the German Munich-based design and manufacturing company Franz Mayer & Co. These are the oldest manufactured by this firm that are preserved in Santiago. They were restored by Juan Alexander Lueiza and Mónica Bahamondes. Stained glass windows portray figures transcendental for the order and for the Fernández Concha family. Thus, facing the altar, on the left hand wall:

– Saint George: Christian martyr and military saint from the 3rd century, who is represented, according to legend, slaying a dragon with his lance.
– Saint Francis Xavier: Spanish Jesuit missionary, known as the Apostle of the Indies. Co-founder, together with Saint Ignatius of Loyola, of the Society of Jesus order.
– Saint Augustine: Priest and Doctor of the Catholic Church. He was the ultimate Christian theologian and philosopher of the first millennium and founder of the Augustinian order.
On the right hand wall:
– Saint Aloysius Gonzaga: Young Italian aristocrat who became a member of the Society of Jesus and renounced any right to his inheritance or status in society to devote his life entirely to the service of God and of needy people. Patron of Christian youth.
– Saint John the Evangelist: The youngest evangelist and, together with Saint Peter, one of the pillars of the early Christian church.
– Child Virgin Mary and her parents: Displays the moment during which a child Mary is being educated by her parents, Saint Anne and Saint Joachim.

At the foot of this stained glass window, the data of registry of the German Munich-based design and manufacturing company Franz Mayer & Co. can be seen.

Altar area follows the same line. Pointed arches dividing the transept area are accompanied by symbolic representations of the four evangelists or as is commonly called: the tetramorphos.

“The man or an angel is Matthew, because his Gospel begins with the genealogy of Jesus, the Christ, the Son of Man.

Mark is represented as the winged lion, as his Gospel begins with John the Baptist and his “voice crying out in the wilderness” like a lion’s roar.

Luke is the winged ox, because his Gospel begins in the Temple with Zacharias – the father of John the Baptist; the ox being a sacrificial animal.

John is represented as an eagle. The eagle is considered as a “sun bird”; a fire, height, depth and light image; it is a bird with a piercing stare, comparable to the “all-seeing eye”; it is the only bird that is able to fly over the clouds and look directly into the sun.”

Thus, the left-hand arch depicts Saint Mark, represented by the lion, and Saint Luke, represented by the ox. On the other hand, the right -hand arch displays Saint Matthew, represented by the man/angel, and Saint John, represented by the eagle.

On the transept right side, there are three stained glass windows manufactured by another firm, possibly a national artisan with a recent date. The greatest is a scene of the Good Shepherd, portraying Jesus surrounded by his flock of sheep. Accompanying the latter, there are two smaller windows representing Saint Mary Euphrasia Pelletier, French Roman Catholic nun, best known as the foundress of the Congregation of Our Lady of Charity of the Good Shepherd; and Sister Mary of the Divine Heart, also a nun from this congregation, who influenced Pope Leo XIII to make the consecration of the world to the Sacred Heart of Jesus.

Apse wall displays a set of three stained glass windows illuminating the altar and two big-size pictorial works. They portray a series related to the life of Jesus, from left to right:

– Virgin Mary and Child, Saint Rose and Saint Dominic: it features an opening of the heavens with the Mother of God holding out Child Jesus to Saint Rose of Lima and Saint Dominic.
– The Holy Trinity: The Father clad in elaborate and luxurious robes with his scepter of command, the Son (Jesus Christ) wearing a gold crown and holding the Cross, and the Holy Spirit as a haloed dove with its wings spread wide in between them. They are standing on a globe that symbolizes the world.
– The Holy Family: featuring an everyday moment of the life of Jesus’ family, where he is cutting a piece of wood with a saw, and Joseph with a hammer and a chisel. On their side, the Virgin Mary is reading a book for them.

The two large paintings accompanying this stained glass window series were created by Italian artist Oreste Rosso, dated 1895. On the left side, there is a representation of the Apparition of the Angel; on the right side, Saint Michael the Archangel. Both were restored by María Eugenia Van de Maele.

It is worth mentioning one of the most treasured objects kept inside the temple and preserved by the congregation: its pipe organ. Manufactured by French luthier Aristíde Cavaillé-Coll, who is considered as the most important pipe organ manufacturer of all times. This was the last and smallest instrument the company made for Chile. In 1894, it was installed by Oreste Carlini, who was the director of the Fábrica Nacional de Órganos. There only remain seven Cavaillé-Coll organs in Chile, all protected by the Council for National Monuments as a Historical Monument.