"There is still a great deal that I want this team to accomplish and I look forward to helping lead us to success in 2018," Grier said in a statement. "I am completely focused and looking forward to building off the success we had this year and want to do even greater things next year."
Named the Big 12 Newcomer of the Year, Grier has thrown for 3,490 yards and 34 touchdowns this season. His touchdown total ranked seventh in the FBS for the regular season.
"Will's decision to return next year certainly makes it a great day for West Virginia football," West Virginia coach Dana Holgorsen said in a statement. "He is a great leader for our program, and I know our fans enjoy watching his talents on the football field. His teammates and the coaching staff are certainly looking forward to his return, and this is positive news for all involved."
The Mountaineers (7-5) will face Utah (6-6) in the Zaxby's Heart of Dallas Bowl on Dec. 26.
Grier missed West Virginia's regular-season finale with a finger injury. The Mountaineers have not announced whether Grier will play against the Utes.