The interior is richly decorated in marble and semiprecious stones, notably a 35 ft (11 m) mosaic of Matthew behind the main altar by Edwin Blashfield.

The first notable funeral Mass offered at St. Matthew's was for Manuel L. Quezon, the president of the Philippines, who died August 1, 1944,[8] and was interred at Arlington National Cemetery until the end of World War II.

Richard, Cardinal Cushing, Archbishop of Boston and a Kennedy family friend, offered a recited (not sung) Pontifical Requiem Low Mass during the state funeral on Monday, November 25, 1963, which was followed by the procession to Arlington National Cemetery in Virginia for the burial.

[15][16] Each year on the day before the term of the Supreme Court of the United States begins, Mass is celebrated to request guidance from the Holy Spirit for the legal profession.

Owing to the cathedral's location in the nation's capital, the Justices of the Supreme Court, members of Congress and the Cabinet, and many other dignitaries (including, at times, the President of the United States) attend the Mass.

The Mass, live-streamed by The Roman Catholic Archdiocese of Washington and televised by EWTN, was celebrated by archbishop Wilton Gregory with no members of the faithful present due to COVID-19 restrictions.