The Browns finished the campaign with a 41-9 drubbing by the Pittsburgh Steelers.
"Although we have made improvements this season, my responsibility is to ensure that we establish a program that will allow this team to compete at a championship level," Browns president Mike Holmgren said in a statement.
"That will continue to be our goal in everything we do."
Mangini, who previously coached the New York Jets, thanked the Browns owners for the opportunity to coach in Cleveland.
(Reporting by Larry Fine; editing by Ed Osmond)