Gunnar S. Gundersen received his earliest education from a drawing course at the ABC school in 1940. The school was an important place for several of the graphic artists, illustrators, and advertising artists of the interwar period. Gundersen distinguished himself early on with a personal style in his designs, and in particular his drawing teacher Scheen was one of those who saw a peculiarity in Gundersen's drawings. Scheen encouraged Gundersen to perfect his talent further, through a closer study of Snorre's royal sagas. For Scheen, the saga had illustrations of the highest quality, and something that he could possibly see similarities to Gundersen's masculine and simplified, decorative form. Scheen, on the other hand, was not particularly impressed by Gundersen's modeling of the body. Gundersen himself is said to have found the act drawing and its anatomical lines to be particularly difficult. On the other hand, he had a flair for portraits, and often with a form of humor or a hint of caricature.

The drawing education ended abruptly in 1941, when Gundersen was placed in a labor camp in Selbu during the Norwegian occupation. He was nevertheless able to practice his drawing through portraits and motifs that were left hanging in the work barracks. The student and drawing teacher kept in touch via letter exchange, and during the period Gundersen stayed at the camp, Scheen pointed out that Gundersen had developed a constructive sense of form, where the drawing is clearly supported by a skeleton that creates the further form. This observation is possibly what we today see as the essence of Gundersen's motif universe.

After a personal crisis, Gundersen had an artistic awakening in 1944, during a trip out into nature. His observations of the sunlight on the water and the mountain's contrasts in purple and black, gave him the inspiration to develop a new and more simplified design language which inspired him to work further within the visual field.

His formal art education was done in the latter half of the 1940s at the Statens Håndverks- og Kunstindustriskole, where he took lessons in the sketching class. Later he took classes at the Norwegian Academy of Fine Arts and attended study trips to Paris.

Although Gundersen worked with both graphics and painting, his art became more overlapping. In the 1960s, he developed a completely unique type of serigraphy. Common to all his motifs in various mediums is a dynamic and strong use of form and colour. The motifs can be seen as rhythmic groupings of different structures. The images are nevertheless organically connected, which gives the motif an overall harmonious express