Galleri Wallner was founded 1974 in Malmö, in the south of Sweden. The gallery soon emerged as one of the major galleries for contemporary art in Sweden. It gained a reputation as one of the most interesting galleries focusing on young artists from Scandinavia, Europe and the US. The gallery has taken part in international art fairs in Amsterdam, Berlin, Cologne, Frankfurt, London and Stockholm. Among the artists who have exhibited with the gallery through the years are Diane Arbus, Curt Asker, Ola Billgren, Max Book, Sarah Beddington, George Brecht, Bård Breivik, Jonathan Borofsky, Barbro Bäckström, John Chamberlain, Enzo Cucchi, Nicola de Maria, Erik Dietman, Cecilia Edefalk, Barry Flanagan, Leonard Forslund, Jens Fänge, Rune Hagberg, Mary Heilman, Per Kirkeby, Paco Knöller, Axel Lieber, Sivert Lindblom, Rita Lundqvist, Eva Löfdahl, Truls Melin, Duane Michals, Henri Michaux, Mimmo Paladino, Irving Penn, Håkan Rehnberg, Carsten Regild, Ulrik Samuelsson, Stig Sjölund, Annika Svenbro, P.G.Thelander, Susanne Weirich, Rolf Wilhelmsson, Per Wizén, Fredrik Wretman and Remy Zaugg.

In 2002 Thomas Wallner assumed responsibility for the exhibitions at Kabusa Konsthall outside Ystad. He collaborated with the founder of Kabusa Konsthall, Lars Lundin, to create what was to become one of the most important exhibition sites in the south of Sweden, known not only for its art but also for its beautiful space and location. During the five years they spent together at Kabusa Konsthall, before it was sold in early 2007, they exhibited among others Torsten Andersson, Filippa Arrias, Jakob Dahlgren, Kristina Eriksson, Anna Finney, John F Franzén, Astrid Göransson, Trond Hugo Haugen, Leif Holmstrand, Bo Hylander, Lisa Jeannin, Hans Jörgen Johansen, Clay Ketter, Oskar Korsár, Noah Lyon, Kristina Matousch, Elina Merenmies, Sirous Namazi, Andreas Poppelier, Nina Roos, Sigrid Sandström, Anders Sletvold Moe, Astrid Svangren and Magnus Wallin.

After this sojourn in Österlen, the gallery moved back to Malmö and established itself in venerable gallery spaces on Adelgatan. Here, over the next three years, many notable exhibits took place, showing the work of artists such as Kristina Eriksson, Anna Finney, Leonard Forslund, Fredrik Lindkvist, Kristina Matousch, Fredrik Norén, Andreas Poppelier, Vesa-Pekka Rannikko, Sigrid Sandström, Anders Soidre, Stina Stigell, Päivi Takala, Martin Thelander and Nichlas Winmalm. During this period, both Vesa-Pekka Rannikko and Sigrid Sandström were also contributing to the Carnegie Art Awards exhibits.

In 2010, Thomas Wallner bought a dairy together with his partner, Gun-Lis Falkman, in the town of Simris in the heart of Österlen. The gallery now has access to fantastic spaces in which to exhibit, the total area of which adds up to 350 square meters.