Loiseau was born in Paris in 1865, where he grew up and studied at the Ecole des Arts Decoratifs. When he was 25 he moved to Pont-Aven in Bretagne to work with Gauguin and other members of the Pont-Aven School. While he was at Pont-Aven, he met and became close with two other post-impressionists, Maxime Maufra and Emile Bernard. The time he spent with these artists led Loiseau to a stronger structure and freer brushstroke in his subsequent work.
He started to exhibit his paintings at the Paris Salon des Indépendants in 1893 and the Salon of La Nationale of1895.
Loiseau traveled considerably in France and became known for his landscapes of the River Seine, the cliffs of Dieppe and the areas around Dordogne valley.