Since 1974 he has led the 10-piece Willem Breuker Kollektief, which performs jazz in a theatrical and often unconventional manner, drawing elements from theater and vaudeville. With the group, he has toured Western Europe, Russia, Australia, India, China, and Japan, the United States, and Canada.
He is also known as an authority on the music of Kurt Weill. In 1997 he produced, with Carrie de Swaan, a 48-hour, 12-part radio documentary on the life of Weill entitled Componist Kurt Weill.
In 1974 he founded the record label BVHaast. Since 1977 he has organized the annual Klap op de Vuurpijl (Top It All) festival in Amsterdam. His scores are published by Haast Music Publishers, which he also operates.
In 1992, the book Willem Breuker, by J. and F. Buzelin, was published in France by Editions de Limon. A Dutch translation was published in 1994 by Uitgeverij Walburg Pers. The book Willem Breuker Kollektief: Celebrating 25 Years on the Road was published by BVHaast in 1999 and includes two CDs
In 1998, Breuker was made a Knight of the Order of the Netherlands Lion.