The Saints hope the move strengthens the depth at a position that could be depleted early next season if starting ends Will Smith and Charles Grant are forced to serve four-game suspensions for violating the NFL's anti-doping policy, which remain on appeal in federal court in St. Paul, Minn.
The 25-year-old Hargrove has had trouble with the NFL's substance-abuse policy, violating it three times. After being suspended for all of 2008, he was reinstated this year.
He worked out for the Saints last week and team spokesman Greg Bensel said Tuesday that New Orleans had signed him and released end Josh Savage.
Hargrove was a third-round draft choice by St. Louis in 2004 and started in 2005. He was traded to Buffalo in 2006.