The Belgian has decided to head back home to be with his family and father Alex who is suffering from pancreatic cancer and may continue his career with a club closer to home.
“Dieter isn’t coming back to the club,” Killie boss Kenny Shiels said.
“It’s a very sensitive situation. He wants to stay with his family in Belgium because his father has only been given a few weeks to live and he wants to be with them in the aftermath of that.
“He did well for us and has his place in Kilmarnock history after scoring in the League Cup Final.
“We’re sad to see Dieter leave but we are compassionate to his needs as he has to look after his family.”