Born in Paris in 1865, Loiseau was apprenticed first to a butcher and in 1880 to a house painter. It was not until 1887, after receiving a small inheritance, that he was able to devote himself to painting. He spent a year studying modelling and design at the Ecole des Arts Décoratifs in Paris and then entered the studio of the French landscape painter Fernand Just Quignon for six months in 1889. He settled in 1890 in Pont-Aven in Brittany, where he met the painters Maxime Maufra and Henri Moret. In 1894 he met Gauguin on the latter’s return from Tahiti, and though he did not accept all of Gauguin’s ideas the encounter led to a stronger structure and freer brushstrokes in his subsequent work.
Loiseau first exhibited his work at the Salon des Indépendants in Paris in 1893, showing also at the Salon de la Société Nationale in 1895 and from 1903 to 1930 at the Salon d’Automne. The contract he received in 1897 from Paul Durand-Ruel gave him the freedom to travel through northern France and the Channel coast, in particular through the valleys of the Oise, the Seine and the Eure, with Pont-Aven as his base in the summers. Just before World War I Loiseau turned to subjects from the Ile de France. Although he continued to travel in the north from the 1920s until his death, he specialized during this period in subjects from the Seine Valley and Paris and also ventured down to the Dordogne region. In his later works he used careful, cross-hatched brushstrokes and a more restrained palette.