The architecture of the Cathedral is an excellent example of the Victorian Gothic period.  The Cathedral measures 120 feet across with twin towers each being 156 feet in height.  The stone used in the exterior of the building is a Connecticut Brownstone, which was the most popular building stone of the Victorian period.

The main altar is made of Verde Issorie, a marble quarried in the French Alps.  The fish, symbol of Our Lord, goes back to the first century A.D.  Above the altar is the testa, one of the most impressive fixtures in the Cathedral.  It weighs 3000 pounds, forming a circle of bronze.  It is used to illuminate and attract attention to the altar below.

The Baptismal Font is located in the recess of the left of the altar its bronze cover incorporates the fish symbol of Christ and the anchor of the State of Rhode Island which symbolized "Hope."  Behind the Baptistery is a seven foot statue of the Blessed Mother and the Christ Child.

The Cathedral Organ, located in the North Transept, is a unique and magnificent instrument.  It was built by the Cassavant Brothers of St. Hyacinthe, Quebec.  It stands 36 feet high and has four keyboards with 56 keys each and a 32 key pedal board.  It utilizes a system called "tracker" which is the oldest type of organ construction.  The tracker system uses a series of rods and levers to control the airflow to each pipe.

Located in the West Tower of the Cathedral are four great bells.  Together they weigh more than four tons.  The bells are named after the four Evangelists: Matthew, Mark, Luke and John.  Each bell carries a prayer and inscription explaining its name and purpose.

The tabernacle was cast in bronze by X. Corberro and Sons of Barcelona, Spain and the inscription beneath it reads, "Food of Angels, Food for Men.:  The artisans who produced the tabernacle spent some 58 hours filing the finial - the small, crown-like top ornament.

The pews of the Cathedral are made of Quartered Appalachian Oakwood.  Seating capacity is 1,452.  The floors of the nave are Travertine marble, while the sanctuary floor is composed of Bottochino marble.

The Cathedral is entered through glass doors, which front Cathedral Square.  The Windows of the Cathedral are a series of stained glass windows fashioned from antique Munich glass.  The windows on the east side of the cathedral depict scenes of God in the Old Testament.  The windows on the west side depict scenes from the life of Jesus Christ in the New Testament.

The great circular window over the main altar in the sanctuary presents 13 scenes of the passion and death of Christ in the tracery openings.  Its dominant colors are variant shades of red and blue.  The west rose window depicts scenes from the life of Our Lady, from the Annunciation to the Assumption.  the dominant color is blue, the color of the Blessed Mother.

In the foyer of the Cathedral, on either side of the front door, are two marble tablets set in memory of Bishop Hendricken, the builder of the Cathedral and Bishop Harkins, the first Bishop consecrated in the Cathedral.

Six Bishops were buried separately in a tomb located beneath the main altar.  The remains of Bishop Tyler, the first bishop of Hartford, were returned to the Archdiocese of Hartford earlier in 2006. The remaining bishops: Bishop Matthew Harkins, Bishop Thomas F. Doran, Bishop Dennis M Lowney & Bishop William A. Hickey were interred with fellow priests in the clergy section at St. Ann Cemetery in Cranston. 

The remains of Bishop Hendricken who was originally entombed in the crypt for 120 years was re-entombed on Friday, December 8, 2006 in a sarcophagus located to the right of the altar along the interior wall of the Cathedral.  The sarcophagus is candeas green Brazilian granite and was obtained from Quality Granite in Pawtucket. Ten men carried the 2,100 pound sarcophagus into the Cathedral. The Bordeaux granite nameplate above the sarcophagus is also from Brazil. Louis Sciolto of Sciolto Memorials was the general contractor for the project. Fr. Anthony Verdelotti, Director of Catholic Cemeteries, designed the sarcophagus.