The Belgian designer has been among those rumored to take over as head designer at Dior. The post has been left vacant since John Galliano was fired last year after a drunken anti-Semetic tirade in Paris last year.
Jil Sander spokesman Jonas Falk said Thursday that a new designer would be appointed to take Simons' place soon. Falk said Simons' exit was by mutual agreement. No further details were given.
Simons' last collection for the label will be previewed Saturday during Milan Fashion Week. The 44-year-old was appointed creative director on July 1, 2005.
The Associated Press contributed to this report.