The former St. Louis Rams coach hasn't signed a contract, but it was expected to happen Thursday.
Spagnuolo became a coaching free agent when he was fired by the Rams on Jan 2.
Spagnuolo was defensive coordinator for the New York Giants for two seasons (2007-08) before coaching the Rams for the last three seasons, compiling a 10-38 record. He has an extensive defensive background, coaching on that side of the ball for eight seasons in Philadelphia under esteemed coordinator Jim Johnson.
The position in New Orleans became available when former coordinator Gregg Williams agreed to take the same position on Jeff Fisher's staff with the Rams, according to league sources. That didn't come as a surprise to Saints coach Sean Payton, who said Tuesday it was apparent before the season ended that Williams was likely to join Fisher.
Spagnuolo's defense in St. Louis ranked 22nd this season, but the unit was stellar against New Orleans, sacking Drew Brees six times and intercepting him twice in the team's most lopsided loss of the season.
Before taking over in St. Louis, Spagnuolo had top-10 defenses with the Giants. His 2007 defense led the NFL with 53 sacks, and the 2008 unit was sixth in the league with 42.
The Associated Press contributed to this report.