Wagemans was born in Brussels in 1877. At the age of thirteen, he attended the Brussels Academy where, under the tutorship of Jean Portaels and Joseph Stallaert, he learned the rudiments of painting in oils. Graduating in 1895, he, along with his fellow artists Alfred Bastien and Frans Smeers, traveled to Paris. He soon became familiar with the works of Fantin Latour and in particular Edouard Manet whose influences were clearly visible in his portraits of this period. By 1900 he had returned to Belgium and in that year first exhibited with the art group, ‘Le Sillon’ followed in 1902 with his debut at the Salon de Gands where he exhibited a painting entitled `Woman in Grey’.
Stylistically his work under went a complete change in 1912 when, after meeting the Luminists Marcel Jeffreys and Rik Wouters, he commenced using a vivid palette full of reds, oranges and blues. This new work was first shown in 1912 at the Galerie G. Giroux in Brussels. During the First World War Wagemans continued to paint having moved to Switzerland to avoid the hostilities. Major shows of his work were held in Switzerland in 1916 and 1917 and again in Brussels after the Armistice in 1919. His work was highly regarded for its force and strength of color and he was honored in France with membership of the Societe Nouvelle des Beaux Arts and in London at the Artists Association.