San Diego State will remain a member of the Mountain West Conference and will not join the Big East this fall.

The Mountain West's Board of Directors voted Wednesday afternoon to reinstate San Diego State this fall. The Aztecs were scheduled to leave the MWC and join the Big East on July 1 as a football-only member and the Big West in all other sports. However, the Aztecs will remain a member of the Mountain West in all sports.

"San Diego State University is pleased to be continuing as a full member of the Mountain West Conference," SDSU president Dr. Elliot Hirshman said in a joint statement released by the MWC. "We are excited about the opportunities our partnership provides for the development of the conference and San Diego State University's athletic programs."

San Diego State's decision comes on the heels of Boise State's Dec. 31 decision to remain in the MWC and not join the Big East as a football-only member.

The Aztecs are the 16th school to announce they were leaving the Big East in the past two years.

With SDSU and Boise State remaining, the MWC will have 12 football members this fall -- Air Force, Boise State, Colorado State, Fresno State, Hawaii, Nevada, New Mexico, San Diego State, San Jose State, UNLV, Utah State and Wyoming.

As far as the Mountain West's divisions, the league's athletic directors and presidents must approve those. Sources told ESPN the most likely would be the six Pacific Time Zone members: Fresno State, Hawaii, Nevada, San Diego State, San Jose State and UNLV; and the six Mountain West time zone members: Air Force, Boise State, Colorado State, New Mexico, Utah State and Wyoming.

Sources also said that the MWC athletic directors and presidents are expected to approve a conference championship game for the upcoming season.

CBS Sports Network will have the option to pick up a Mountain West Championship game.

"We've been talking to them [CBS Sports Network] every step of the way," MWC commissioner Craig Thompson said.

Thompson said the league hopes to have a conference schedule completed by late April.

"I'm elated with our 12-team lineup," Thompson said. "We got the band back together."

On Jan. 8 in Miami, Thompson told ESPN that his league's presidents must vote by a three-fourths majority to approve San Diego State's return to the league.

That approval came Wednesday afternoon.

"With today's announcement, SDSU's membership continues uninterrupted and helps the Mountain West maintain a solid foundation going forward," Thompson said in a statement.

And because Boise State changed its mind about joining the Big East, the Aztecs will not have to pay an exit fee to leave the Big East. In SDSU's contract with the Big East, the Aztecs' exit fee is withdrawn if there was not another Big East member located west of the Rocky Mountains.

When Boise State announced Dec. 31 it wasn't joining the Big East, San Diego State athletic director Jim Sterk said the Broncos' decision "represents a significant change in conference realignment."

San Diego State joins Boise State and TCU as schools that signed contracts to join the Big East only to change their mind before actually ever playing in the Big East.

"On behalf of the BIG EAST Conference Presidents and Directors of Athletics, I want to wish San Diego State the best," Big East commissioner Michael Aresco said in a statement. "We have enjoyed working with President Elliot Hirshman and Director of Athletics Jim Sterk and our membership has the highest regard for them and for their institution."

On Jan. 8, Aresco told ESPN that if his league lost San Diego State, it would remain at 10 football members -- Cincinnati, Houston, Louisville, Memphis, Rutgers, SMU, South Florida, Temple, UCF and UConn -- for this fall.

In 2014, East Carolina and Tulane will join the Big East to replace Louisville and Rutgers, who are leaving for the ACC and Big Ten, respectively. Aresco said it was "unlikely" ECU or Tulane would join the Big East in 2013. ECU, which was originally sought as a football-only member, is now expected to become an all sports member in 2014.

Navy is scheduled to join in 2015 as a football-only member, giving the Big East 11 football members. Tulsa is being targeted to become the Big East's 12th member in 2014, sources told ESPN.

The Big East's seven Catholic basketball schools -- DePaul, Georgetown, Marquette, Providence, St. John's, Seton Hall and Villanova -- announced last month they were leaving the league. However, their departure date has not been determined.

Notre Dame, a Big East member in all sports but football, also announced last year it was leaving for the ACC. The Fighting Irish's departure date also is unknown.

ESPN.com's Andrea Adelson contributed to this report.