The 25-year-old middle linebacker led the Falcons in tackles last season with 147. He also had a career-best two interceptions, returning one for a touchdown.
"Curtis is a versatile, hard-working player that has displayed a knack for being around the football, and more importantly, making plays on the ball," Saints general manager Mickey Loomis said in a statement released Saturday night. "He has the ability to play all three linebacker positions and we feel that he's just entering the prime of his career. We think he can come to New Orleans and fit in well and provide us with a significant contribution to our defense."
Lofton started all but one game his rookie season, working mainly in the team's base package, and he's been an every-down player the past three years. He also led the Falcons in tackles in 2010, registering 142.
Except for a brief stint at outside linebacker early in his college career at Oklahoma, Lofton always has been in the middle of the defense.
The Saints were recently punished by the NFL for a bounty system, and Jonathan Vilma's name appeared in the report by the league. Commissioner Roger Goodell has said he will deal with player punishment at a later date.
Information from The Associated Press was used in this report.