San Francisco-based American architect Arthur Brown, Jr. designed the auditorium as well as the two buildings adjacent to it.
The architectural style of the building is Neoclassical, as are all the buildings in the Federal Triangle development.
The portico of the Auditorium provides the motif for the both buildings which are on either side of it.
Six Doric columns form the auditorium's portico.
Over the portico is a pediment titled "Columbia", by Edgar Walter.
The sculpture on the pediment depicts Columbia (the feminine personification of the United States) seated on a throne-like chair, an eagle on her right, a nude youth on her left, and the rays of the sun spreading out behind her.
Behind the portico, a second pediment sits over an archway which leads to the colonnade.
This sculpture, by Edmond Romulus Amateis, depicts George Washington at the Battle of Trenton.
The interior is in the Beaux Arts style.
The interior lighting was designed by Brown, and consists of brass and aluminum chandeliers overhead and aluminum and gold leaf bracket lamps on the walls.
The ceiling was originally painted blue.

Colonnades link the auditorium to the buildings to the east and west, and galleries in the Auditorium's rear provide interior passages to these buildings as well.
 The galleries have received much praise.
One critic noted, "The open galleries linking the auditorium to its neighbors constitute one of the greatest passages in American architecture."

The entire structure has been called "one of the most magnificent auditoriums in the country."
San Francisco-based American architect Arthur Brown, Jr. designed the auditorium as well as the two buildings adjacent to it. The architectural style of the building is Neoclassical, as are all the buildings in the Federal Triangle development. The portico of the Auditorium provides the motif for the both buildings which are on either side of it. Six Doric columns form the auditorium's portico. Over the portico is a pediment titled "Columbia", by Edgar Walter. The sculpture on the pediment depicts Columbia (the feminine personification of the United States) seated on a throne-like chair, an eagle on her right, a nude youth on her left, and the rays of the sun spreading out behind her. Behind the portico, a second pediment sits over an archway which leads to the colonnade. This sculpture, by Edmond Romulus Amateis, depicts George Washington at the Battle of Trenton. The interior is in the Beaux Arts style. The interior lighting was designed by Brown, and consists of brass and aluminum chandeliers overhead and aluminum and gold leaf bracket lamps on the walls. The ceiling was originally painted blue.
Colonnades link the auditorium to the buildings to the east and west, and galleries in the Auditorium's rear provide interior passages to these buildings as well.  The galleries have received much praise. One critic noted, "The open galleries linking the auditorium to its neighbors constitute one of the greatest passages in American architecture."
The entire structure has been called "one of the most magnificent auditoriums in the country."
Andrew W. Mellon Auditorium