He will have two years of eligibility remaining.
Warmack, a former U.S. Army All-American, appeared in 16 games in his career at Alabama. He did not see the field last season.
At Oregon, he'll reunite with his former position coach at Alabama in Ducks first-year head coach Mario Cristobal.
"I am going to play my last two years for the coach I believe in the most!" Warmack wrote. "Coach Cristobal let's take Oregon to the highest level!"
Oregon has leaned heavily on the transfer wire this offseason, adding former Wake Forest receiver Tabari Hines, former UNLV cornerback Tim Hough and former USF tight end Kano Dillon.