He has appeared in many of the world's well-known opera houses, including the Metropolitan Opera, San Francisco Opera, Lyric Opera of Chicago, Houston Grand Opera, Seattle Opera, Dallas Opera, Opera Company of Philadelphia, Pittsburgh Opera, Royal Opera House (Covent Garden), Paris Opera, Bayerische Staatsoper, Glyndebourne Festival, and the Theatre Royal de la Monnaie in Brussels. He has also appeared at the Mostly Mozart Festival. In 2011, Gunn was featured in the Mormon Tabernacle Choir's annual Christmas concerts to 80,000 person crowd and broadcast on PBS. An album was released in 2012 entitled Once Upon a Christmas.
While he is noted for his vocal prowess and acting, Gunn has received almost more fame for his physique, a peculiar feat for an opera singer. In 2008, he was featured in People magazine's list of "The Sexiest Men Alive."
Gunn was appointed a tenured professor of voice at the University of Illinois, beginning in the fall semester of 2007. His wife, Julie Jordan Gunn, who holds a doctorate (A. Mus. D.) in Vocal Coaching & Accompanying from University of Illinois, was also appointed Associate Professor in collaborative piano at the University of Illinois.
- Paul in Amelia
- Title role in Billy Budd
- Title role in Hamlet
- Lancelot in Camelot
- Guglielmo in Così fan tutte
- Figaro in Il barbiere di Siviglia
- The Count in Le nozze di Figaro
- Marcello in La bohème
- Harlekin in Ariadne auf Naxos
- Papageno in Die Zauberflöte
- Zurga in Les pêcheurs de perles
- Prince Andrei in War and Peace
- Valentin in Faust
- Riolobo in Florencia en el Amazonas
- Clyde in An American Tragedy
- Buzz Aldrin in Man on the Moon by Jonathan Dove
- Created the role of Father Cayetano Delaura in Love and Other Demons (2008)
- Ravenal in Show Boat
- The Lodger in The Aspern Papers (opera)
- Billy Bigelow in Carousel (musical) at Live from Lincoln Center
- Danilo in The Merry Widow
- U.S. Public Records Index Vol 1 (Provo, UT: Ancestry.com Operations, Inc.), 2010.
- Metropolitan Opera International Radio Broadcast Information Center. Nathan Gunn, Baritone
- Lacher, Irene (November 29, 2009). "Opera barihunks hit a muscular note". Los Angeles Times. Retrieved February 4, 2014.
- People Magazine's sexiest men alive