Saints head coach Sean Payton and general manager Mickey Loomis had been mostly silent about whether Ryan would return for a third season.
The Saints have already dismissed three assistants since the end of the season, which ended with a 7-9 record. In Ryan's first season, in 2013, the Saints ranked fourth in total defense and gave up 19 points per game.
This season, the defense ranked next to last in the league and surrounded almost 27 points a contest, giving up 30 or more points eight times.
Saints defenders have said they wanted Ryan back in for next season.
"I don't want to play for any other defensive coordinator other than Rob Ryan," linebacker Curtis Lofton said.
"I want him back," cornerback Keenan Lewis added. "I'm going to ride with him, 100 [percent]. He's a great coordinator. You just can't blame him when things go wrong. We're the ones out there playing."
- Scooby Axson