The contract will pay Mathis $3.5 million in total and $2 million this year, ProFootballTalk's Mike Florio reports.
Mathis will be 35 at the start of next season. He has spent the last two seasons in Detroit after playing the first 10 years of his career with the Jacksonville Jaguars.
While speaking with reporters at last month's NFL combine, Lions general manager Martin Mayhew praised Mathis's ability to mentor young players.
“We’d love to have Rashean back,” Mayhew said, according to the team's website. “I mean he’s really been a good leader for us. He’s done a phenomenal job, I think, working with Darius Slay.”
Mathis started all 16 games for the Lions in 2014 and finished the season with 42 tackles and one interception, which he returned a touchdown.
- Josh Sanchez