Søndergård studied percussion and timpani at the Royal Danish Academy of Music from 1989 to 1992, where his teachers included Gert Mortensen. From 1989 to 1992, Søndergård was a timpanist in the European Union Youth Orchestra. He joined the Royal Danish Orchestra as a timpanist in 1992. He served on the faculty of the Royal Danish Academy of Music from 2001 to 2002.
Søndergård devoted greater attention to conducting from age 27. His conducting mentors have included Alexander Polianichko, Yves Abel and Graham Bond. His conducting work in contemporary music has included conducting the 2005 premiere of Poul Ruders' Kafka's Trial with the Royal Danish Opera, in performances which were recorded for commercial release. Søndergård became principal conductor of the Norwegian Radio Orchestra (KORK) in 2009, and concluded his KORK tenure after the 2011-2012 season.
Søndergård first conducted the BBC National Orchestra of Wales (BBC NOW) in December 2009, as an emergency substitute for Thierry Fischer. In July 2011, Søndergård was named the 14th principal conductor of the BBC NOW, effective with the 2012-2013 season, for an initial contract of 4 years. In February 2016, the BBC NOW announced the further extension of his contract as principal conductor through "at least 2018". Søndergård formally concluded his tenure as principal conductor of the BBC NOW is July 2018.
Søndergård first guest-conducted the Royal Scottish National Orchestra (RSNO) in 2009. as an emergency substitute for Yakov Kreizberg. In October 2011, the RSNO named him its principal guest conductor, effective with the 2012-2013 season, with an initial contract of 3 years for 3 programmes per year. In May 2017, the RSNO announced the appointment of Søndergård as its next principal conductor, effective with the 2018-2019 season.
- Karen Price (2011-07-15). "Scandinavian cool: conductor Thomas Søndergård". Western Mail. Retrieved 2011-07-31.
- Andrew Clements (2005-03-15). "Kafka's Trial (Opera House, Copenhagen)". The Guardian. Retrieved 2011-07-31.
- Anthony Tommasini (2005-03-14). "Kafka on Trial, Opera Fans in Heaven". New York Times. Retrieved 2011-07-31.
- Andrew Clements (2006-06-30). "Ruders: Kafka's Trial, Van Hall/ Stille/ Rorholm/ Jensen/ Royal Danish Opera/ Sondergard (Da Capo, two CDs)". The Guardian. Retrieved 2011-07-31.
- Jan Frederik Heyerdahl (2008-02-12). "KORK under dansk ledelse". Norwegian Radio. Retrieved 2011-07-30.
- Fred Olav Vatne (2011-07-12). "KORK må finne ny sjefdirigent". Norwegian Radio. Retrieved 2011-11-06.
- "BBC National Orchestra of Wales announces new Principal Conductor" (Press release). BBC. 12 July 2011. Retrieved 2011-07-31.
- Peter Collins (2011-07-12). "Great Dane to be chief BBC National Orchestra Wales conductor". Western Mail. Retrieved 2011-07-31.
- "BBC National Orchestra & Chorus of Wales' Principal Conductor Thomas Søndergård extends his contract" (Press release). BBC. 15 February 2016. Retrieved 2016-02-18.
- Tim Ashley (2018-07-23). "BBCNOW/Thomas Søndergård review – bowing out in style". The Guardian. Retrieved 2018-07-24.
- "Thomas Søndergård joins RSNO Artistic Team" (Press release). Royal Scottish National Orchestra. 18 October 2011. Retrieved 2011-11-06.
- Keith Bruce (2017-05-25). "RSNO names its new Music Director". The Herald. Retrieved 2017-05-26.
- Anthony Tommasini (2011-06-10). "Poul Ruders". New York Times. Retrieved 2011-07-31.
- Fiona Maddocks (2015-04-12). "Sibelius: Symphonies 2 & 7 CD review – intense and rigorous". The Observer. Retrieved 2016-02-18.
- Askonas Holt agency biography of Thomas Søndergård
- DaCapo Records English-language biography of Søndergård
- Dansk Kapelmesterforening (Danish Conductors Association) page on Thomas Søndergård
- Laura Sinnerton, "Thomas Søndergård joins BBC NOW as principal conductor". BBC Wales Music blog, 12 July 2011
- Rhodri Lewis, "New conductor for BBC National Orchestra of Wales". BBC News Wales, 12 July 2011
- Caroline Rigby, "BBC National Orchestra of Wales plays for new conductor". BBC News Wales, 13 July 2011
| Principal Conductor, Norwegian Radio Orchestra
| Principal Conductor, BBC National Orchestra of Wales