"Hey Valley High," he told students. "I used to be a Viking."
Mann, now 56, played in the NFL from 1983 to 1995. Most of his career was spent with the Washington Redskins before playing a season for the San Francisco 49ers.
He played in four Super Bowls and won three of them.
He visited his alma mater to encourage and motivate as many students as he could.
"I want to be impactful at whatever I do, and wherever I go, and whatever I say, and whoever I interact with. So, I am hoping that something I said today makes a difference," Mann told FOX40.
Mann's left hand is permanently deformed after years of chasing quarterbacks. He's had 15 knee surgeries and a hip replacement, but he says his sacrifice has been worth it.
Saturday, Mann will be inducted into the Sacramento Sports Hall of Fame.
"Hopefully, this is the momentum I needed to go because I've also been nominated for the D.C. sports hall of fame, so hopefully, the NFL hall of fame is next," he said.