The surgery will be performed by Dr. Lewis Yocum, who will also remove any non-healthy tissue from the labrum in Bedard's left shoulder. A timetable on Bedard's recovery will be announced following the surgery.
"Erik has worked diligently with our medical staff for the past two months attempting to rehabilitate his shoulder without surgery," said Lee Pelekoudas, the Mariners' vice president and general manager of baseball operations. "We have determined that surgery is the best course of action at this time."
Bedard underwent an MRI on July 22 and was examined by Dr. Edward Khalfayan, the Mariners' medical director.
Bedard made 15 starts this year, compiling a 6-4 record and a 3.67 ERA.
Manager Jim Riggleman said the decision for Bedard to have the surgery was the "last option" designed to get Bedard ready for next year.
"Erik explored all the opportunities to throw," Riggleman said. "He just wasn't really feeling good enough that he could get on the mound and pitch."
Robert Falkoff is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.