The band consists of Maarten Devoldere, Jinte Deprez, Simon Casier, Michiel Balcaen, and Tijs Delbeke, who all come from the areas of Kortrijk and Ghent (Flanders).

In the spring of 2005, Devoldere, Vanneste, and Deprez (aged 18 at the time) won the national Kunstbende competition for young people with the song "Lost and Found".

In early 2007, after sixty performances, bassist Joachim Quartier and drummer Koen Verfaillie were replaced by Simon Casier and Christophe Claeys.

The single was picked up by Radio 1 and Studio Brussel and lingered through the summer in the De Afrekening hitlist, winning second place.

In the summer of 2009, Balthazar went to South Africa for a club tour and then began work on their first studio album, titled Applause.

[11] The Thin Walls tour stretched over the whole of Europe, with Balthazar playing at many big concert halls and festivals in Belgium, France, the Netherlands, United Kingdom, Italy, Switzerland, Turkey, and Ukraine.

[12] Balthazar's song "The Man Who Owns the Place", from their 2012 album Rats, plays during the opening credits of Season 1 of the Belgian TV series The Break (La Trêve), and "True Love" from their 2015 album Thin Walls plays during the opening credits of Season 2.

[13] Writing for Beats Per Minute, John Amen commented, Sand offers "captivating vocal performances" and "exemplary hooks", Balthazar actualizing "the potential displayed on earlier projects, distinguishing themselves in a genre packed with talented creators".

[14] The cover of the album features Zhdun, an anthropomorphic statue by Dutch sculptor Margriet van Breevort.