Withers, 18-7 with two playoff appearances in two seasons at James Madison, will take over at Texas Staet for Dennis Franchione, who stepped down after a 3-9 season in 2015.
Texas State will be entering its fifth season in FBS in 2016.
JMU athletics director Jeff Bourne said Wednesday that a national search to replace Withers is under way.
“While we are disappointed to see Coach Withers depart, we are grateful for what he accomplished in his two years at James Madison and excited for the future of our program,” Bourne said.
Losing Withers to a job that is at best a lateral move for him has to sting the JMU athletics program. The Bobcats play in the Sun Belt Conference, the hinterland of FBS, and averaged 18,166 fans per game at home in 2015.
For comparison, JMU has averaged more than 21,000 fans per game at home over the past five seasons.
Withers replaced Mickey Matthews, who was fired after a tenure that included a national title in 2004 and a win at Virginia Tech in 2010, in December 2013.
JMU will engage CarrSports during the hiring process to appoint a new head coach, according to a release from the athletics program. CarrSports assisted with the hiring of Everett Withers in 2013 and also worked with the university on its FBS Feasibility Study.
“We are confident that there are candidates available who will fit the characteristics of this institution, provide a comprehensive college experience to our student-athletes and continue the history of success for this program,” Bourne said.