The church's interior was renovated in 1986, but the sanctuary retains much of its early decoration, including Georgian marble columns, Numidian marble walls, a semi-dome ceiling, Stations of the Cross, stained glass windows, religious paintings by Tadeusz Żukotyński, a sculpture by Harry Breen, and other works of art.

Saint Mother Théodore Guérin, the foundress of the order, described the primitive chapel to friends in France, "The Church!

Although Bohlen's frame chapel was large, capable of seating 300 people, it was only intended to be a temporary structure until a more substantial church could be erected at Saint Mary-of-the-Woods.

By June 1892 the plasterwork was completed and installation of temporary wooden flooring, seats, and altars permitted the sisters to worship in the unfinished church.

"[1] Mother Mary Cleophas and General Councilor Sister Mary Alma Ryan, who traveled to Europe to visit numerous churches and gather ideas, were inspired by the Basilica of Sant'Apollinare Nuovo in Ravenna, Italy, and the Cathedral Church of the Holy Trinity, Paris, among others.

[1][5] The completed church was consecrated on October 23, 1907, in a celebration attended by religious dignitaries, including Francis Silas Chatard, Bishop of the Diocese of Indianapolis.

[3][5] The Church of the Immaculate Conception is constructed of Indiana limestone and designed in the Italian Renaissance Revival style.

[7] Architect Oscar D. Bohlen explained that the church was designed in an "Italian Renaissance style with a French sentiment.

[3][4][7] The varied types of marble that decorate the church come from Italy, Africa, Skyros, Greece and the United States.

The original reredos (high altar) has been removed, but the sanctuary still contains religious artifacts, paintings, sculptures, stained glass windows, and other works of art.

[3][12] Tadeusz Żukotyński (Thaddeus von Zukotynski) of Munich and Chicago painted three murals in addition to the sanctuary's semi-dome fresco.

The east and west transepts and the arcade beneath the dome include Żukotyński's of the Four Evangelists, the "Return from Calvary," and the "Flight into Egypt."

[4] Removal of the reredos opened a space in the center wall of the sanctuary for a sculpture by Harry Breen of Champaign, Illinois.

It is placed in front of a shrine that contains the tomb of Saint Mother Théodore Guérin, foundress of the Sisters of Providence of Saint-Mary-of-the-Woods.

[3] In the upper balcony at the west front of the church is a rare pipe organ made by the Casavant Frères Company of Canada and installed in 1953.

Hours of worship are 11 a.m. on Sunday; Monday through Saturday at 11:30 a.m. (Exceptions: funeral Masses, special feasts, and holy days).