Jonas was born in the town of Anzin in northern France. He first studied in Valenciennes with the painter Layraud, then in Paris at the École des Beaux-Arts under Albert Maignan, Léon Bonnat and Henri Harpignies. He exhibited at the Salon des Artistes Français and was elected to its membership in 1904. He won a number of awards and prizes, including a silver medal and the second Prix de Rome in 1905, a gold medal and a traveling fellowship in 1907. In 1911 he won the Prix National at the Paris Salon. He won a medal for his printmaking in 1935 and was elected to the Salon jury for both painting and engraving in 1945. He was made a Knight of the Legion d’honneur in 1929.
Jonas came to prominence during the First World War as one of the greatest and most prolific of war artists. He was mobilized at the end of 1914 and in February of 1915 was attached to the Musée de l’Armée in Paris as an official military painter. As such, he often traveled to the front lines making paintings and drawings that were later published in newspapers, magazines, and books throughout the world. Many of his drawings and paintings of the war were published in the weekly Parisian newspaper, Illustration, perhaps the most widely read newspaper in France. He also became known for his striking portraits of officers and soldiers, and after the war he illustrated a three-volume history of the Great War titled The War as Told by Our Generals. He was a skilled mural painter and his works adorned a number of buildings in Paris and elsewhere.
Jonas concentrated on realist subjects. He illustrated a number of books, including works by Molière, Daudet and Balzac. According to Bénézit, Jonas “trained in an academic style, he quickly developed his own approach in every area, showing a vigorous drawing technique, a psychological awareness of his many portrait subjects, and a luminosity in his landscapes and domestic interiors. He remains a true master of line and his work continues to serve as a reference for many artists. Although he did not belong to any 20th-century avant-garde movement, Jonas’s work displays an understanding of Japonism, Impressionism and Fauvism in the use of broad brushstrokes in beach and street scenes, and even portraits, and a fondness for luminous colors.”
A retrospective of Jonas’s work was held in Paris in 1992. In 2003 the exhibition Lucien Jonas and Mural Painting in Paris in the 1930s was held at the Musée Carnavalet. His work can be found in numerous public collections, including the Metropolitan Museum of Art, the Musée Carnavalet, the Musée de l’Armée and the Musée du Petit Palais.