The team says Clemons is departing after 27 seasons with the Lions. He was a defensive assistant in 2011.
He's worked for nine head coaches with the Lions and coached multiple positions on defense. He's also served as the team's strength coach.
Before joining the Lions in 1985, Clemons was strength and conditioning coach at Arizona State and a linebackers coach at New Mexico State. He also coached outside linebackers at Kutztown University.
"I've really enjoyed every part of it and I've been lucky to do it this long at any level," Clemons told the site. "I would have been happy to be at Northern Lehigh High School this long."
According to the site, Clemons will stay with the team until the end of the NFL combine.
The Associated Press contributed to this report.