Jacky June began studying piano at age six. In 1943, he joined the Henry Van Bemst (born 1916) Orchestra. After World War II, June founded and directed his own jazz orchestra at the Hotel Cosmopolite Bruxelles. He also played with Hot Club de Belgique and the The Kot Jazzmen, the latter from which, in the 1950s, his Jump College Orchestra emerged.
In 1951, he performed with Roy Eldridge at Jazzclub La Rose Noire. Jazz critics compared June's style to that of Sidney Bechet and Benny Carter, both with whom June recorded, along with René Thomas, Jean Blaton, Peanuts Holland, Don Byas and Léon Demeuldre in 1965, and perhaps in 1967 and 1971
In the 1950s, his Jump College Orchestra fronted Charles Trenet and Marlene Dietrich at the Knokke Casino and Sidney Bechet at the Palais des Beaux-Arts.
The Kot Jazzmen was founded during the Nazi occupation of Belgium, when a number of Brussels musicians went into hiding and got together in a tiny four-story building on the Rue des Moineaux. The house became famous as Le Kot (the Digs). The group included:
Léon "Podoum" Demol (tp),
Jacky June (woodwinds),
Léon "Bodash" Demeuldre (drums),
Herman Sandy (trumpet),
Jacky Thunis (drums) and
Jean Warland (double bass).