Paul Welsch was born on July 26, 1889 in Strasbourg, 7 rue des Juifs. The family then moved to 7 rue de Wissembourg before settling in 1920 at 5 rue du Conseil des Quinze. Paul Welsch began his secondary studies at the secondary school Fustel de Coulanges, which he continued in 1907 in Hanover, where he already felt very attracted to painting. He turned to law studies in Strasbourg, then studies in political science in Paris (1909-1911). At this time, he became a pupil of Émile Schneider (1873-1947) in Strasbourg with whom he presented his first essays. In Paris, in 1911, he began painting with Maurice Denis (1870-1943) who convinced him to devote his life to fine arts. He definitely took the plunge in 1912. He perfected his skills in engraving and drawing with Bernard Naudin (1876-1946). Until 1914, he studied at the Académie Ranson with Maurice Denis and Paul Sérusier (1864-1927). He also took engraving lessons with Maurice Achener (1881-1963) with whom he exhibited in Paris (1912, 1913) and Chicago (1914,1915).

In 1919 he formed with other painters (Jacques Gachot, Hans Haug, Edouard Hirth, Martin Hubrecht, Luc Hueber, Louis-Philippe Kamm, Simon Lévy, Charles Schenckbecher and Lisa Krugell)  May's Group, influenced by the works of Paul Cézanne: exhibitions in Paris (Bernheim-Jeune, 1921) and Strasbourg (Maison d'Art Alsacienne, 6 rue Brûlée, until 1934). After the war, he settled permanently in Paris (152 rue Broca then 88 rue Bonaparte). In 1920 he illustrated his first book, Les Bourgeois de Witzheim by André Maurois. The same year, he spent eight months in Tunisia which he transcribed in a sober, serious and luminous painting.

He first stayed in Saint-Tropez with his friends Hugues. He kept going there  regularly. His painting became quite geometric with frank colors. He also went to Cagnes and then to Corsica (1925). In 1922 he was seen in Italy (Florence, Naples) where he developed a passion for Renaissance painting (Masaccio, Giotto, Piero della Francesca). He exhibited at the Salon des Indépendants and became a member of the Salon d'Automne in Paris. He illustrated his second book in 1923, Amis et amiles and Asseneth, two tales from the Middle Ages transcribed by Fernand Fleuret.

From 1924, Paul Welsch gradually gave up  this emphasized geometry in his canvases for flexible and simplified lines, characteristic of his style.

He participated in the Decorative Arts exhibition in Paris in 1925 with two panels for the Pavillon d'Alsace: Water and Earth.

Alongside the landscapes of the South, the artist turns to the more muted shades of Paris and Alsace. However, he does not neglect still life and nude. This is the period when browns and blues dominate in his paintings, very strong austerity in the paintings of Quercy (stays in Puylaroque in 1927 and 1928). Similarly, the portraits of this period, on a very bare background, are those of women with sad faces (for example Woman in a Red Vest [1929] from the MAMC in Strasbourg) softened by the suppleness of the lines and the art of colours correspondence.

During the 1930s, Welsch definitively establishes this poetic realism which is characteristic of his art. He exhibited at the Berthe Weill gallery, participated in the political life of his time (wall decoration for the Colonial Week of 1932, illustration of Megglé's books on the AOF [French West Africa], the AEF [French Equatorial Africa] and Syria, drawings of the events of February 6, 1934 Place de la Concorde in Paris, Saar land plebiscite, etc.).

After several stays in Obernai in Alsace (1935-1939), he was mobilized on the Lorraine front before being taken prisoner from 1940 to 1941 in the XVII  Edelbach and V.a Weinberg oflags from which he brought back many sketches. He spent a large part of the rest of the war in Dordogne, in Génis, in Périgord Vert. The oil paintings he produces there endlessly decline the range of greens, one of his favorite colors, an undoubtedly legacy from Cézanne.

During the post-war period, in addition to Paris and Strasbourg, it will be seen in the South (Saint-Tropez, Sanary, Malaucène in Vaucluse). His latest works, in a style close to the 1930s, are however characterized by a wider range of warm colors. Paul Welsch produced numerous lithographs in parallel, mainly in black and white but also in color (Le Rendez-vous des chasseurs, Salon d'Automne de Paris 1949).

He drew the illustrations for four books: Little poems in prose by Baudelaire (1947, apparently unpublished), Le Pilier des Anges by Claude Odilé (1948), Sketches of Provence by André Suarès (1952) and La Bonne chanson by Verlaine (1954). For these last two works, he embarked on the technique of wood engraving. In 1953, he produced another vast mural for the Hotel Technical College of Strasbourg (currently Fustel de Coulanges College) which summarizes his universe: the simple life of man in nature. He died of lung cancer on June 16, 1954 in Paris and was buried in  Saint-Gall cemetery in Strasbourg.