The pick was announced at a gala dinner in New York, during which Manziel got the nod over Kansas State quarterback Collin Klein and Notre Dame linebacker Manti Te'o.
Manziel earned the media nickname "Johnny Football" as he set an SEC record for total offense by amassing 3,419 passing yards and rushing for 1,181 more while accounting for 43 touchdowns -- 24 through the air.
The signal-caller's efforts helped produce Texas A&M's 10-2 record and a trip to the Cotton Bowl.
The highlight of Manziel's season came when he paced the Aggies to a Nov. 10 win over then-No. 1 Alabama.
Te'o -- a keystone of the undefeated Irish team that will play for the national championship in January -- would have been the first pure defensive player to receive the trophy in its 78-year history.
Klein, meanwhile, led Kansas State to an 11-1 record and completed 15 touchdown passes.