From the age of twelve he played the organ in the church of Saint-Mard in Virton. In 1916, he entered the episcopal minor seminary of Namur (located in the abbey of Floreffe) and deepened his musical training with the organist Louis Lejeune, with René Barbier and Auguste Verrees (1884-1957). Ordained a priest in 1922, he was sent to Bertrix as a vicar. Three years later, his diocese authorised him to continue his musical training in Paris. At the Gregorian Institute and the Schola Cantorum, he studied with Louis Vierne (organ and improvisation), Guy de Lioncourt (counterpoint) and Vincent d'Indy (composition). During these years, he was also Henri Mulet's substitute at the Saint-Philippe-du-Roule organ.

Back in Belgium in 1929, he was appointed singing teacher and choirmaster at the seminary of Floreffe where he developed an intense cultural activity. Several artists he had known in Paris stayed at the Abbey: Charles Tournemire, Joseph Bonnet, Henri Ghéon and Henri Brochet. Among his most brilliant pupils during this period was Pierre Froidebise.

"If Abbé Jacquemin's influence was so profound, it was because he made souls sing in harmony with his own and thus raised them in beauty to God" - Canon Kaisin

"Many of his disciples in the clergy, in the cloisters, and also in the world, acknowledge that they owe him much of the best that they have in them1" - Mgr André-Marie Charue, Bishop of Namur.

With the war, the artistic and cultural life in Floreffe slowed down. The exodus had a painful influence on his health. Appointed parish priest in the village of Mont-sur-Meuse in 1941, Jacquemin suffered from depression. At the end, his state of mind was one of luminous and pacifying hope. He died prematurely at the age of forty-seven.

Charles Tournemire dedicated the twelfth office of his Orgue Mystique (La Septuagésime) to him.