In 1982 he published his first picture book "Das Elefantentreffen oder 5 dicke Angeber", which was very well received. In addition to many picture books with his own texts, he has illustrated children's books ("Der neue Pinocchio" by Nöstlinger), poems (Josef Guggenmos), stories and fairy tales by the Brothers Grimm and H. C. Andersen. He has also worked for the magazines "Der Rabe" and "Der Bunte Hund" and drawn many cover illustrations, most recently for the Artemis Fowl books.
Nikolaus Heidelbach's works have received many awards. For his complete works he was awarded the special illustration prize on the occasion of the Deutscher Jugendliteraturpreis in 2000.