The French tennis federation (FFT) announced on Thursday that Simon would play without a coach, having worked with Tulasne since February 2007.
They announced on the FFT website: "Gilles Simon and Thierry Tulasne, his coach, have decided by common accord to put an end to their collaboration.
"The Nice man ... wishes to fly with his own wings."
Simon, 27, reached sixth in the world in January 2009 and won 10 ATP tour titles with Tulasne as his coach.
The FFT said they were ready to help Simon "put in place his new sporting project".