The Panthers gained a weapon for a rookie quarterback in Thielen, 32, as the 10-year NFL veteran comes in with a load of experience from his time with the Vikings.
Here are five things to know about him.
1. Pro Bowl seasons in Minnesota: Thielen's strongest statistical seasons came in 2017 and 2018, the two years he received a Pro Bowl nod and totaled over 1,000 receiving yards.
Paired with quarterback Case Keenum in 2017, Thielen totaled 1,276 yards on 91 catches with four touchdowns, as the Vikings made it to the NFC championship game. In 2018, Thielen put up a career-high 1,373 yards on 113 receptions with nine touchdowns, catching passes from Kirk Cousins.
He continued to play for the Vikings through 2022, putting up 716 yards on 70 catches while playing in all 17 games last season.
2. Career records: Thielen owns two NFL records broken in the 2018 season. He started the year with eight straight games of more than 100 receiving yards, tying Calvin Johnson's record for the most consecutive games with 100 receiving yards. He also set the record for the most consecutive games with 100-plus receiving yards to begin a season.
After starting the year with 925 yards in eight games, the streak ended in Week 9. He finished the year with a career-best 1,373 receiving yards.
3. First touchdown against the Panthers: Thielen's first NFL touchdown came in 2014 when he blocked a punt from Carolina's Brad Nortman and brought it 30 yards to the end zone. He won NFC Special Teams Player of the Week honors after that game.
4. Making the Vikings from a rookie tryout: An undrafted prospect out of Minnesota State University, Mankato, Thielen made his mark at a rookie tryout and evaluation with the Vikings in 2013. He spent his first season in the league on Minnesota's practice squad before earning a spot on the 53-man roster ahead of the 2014 season, thanks partly to solid preseason performances on offense and special teams.
5. Walter Payton Man of the Year nominee: Thielen was the Vikings' nominee for 2022's Walter Payton Man of the Year Award. Thielen and his wife, Caitlin, founded the Thielen Foundation in 2018, focused on youth development programs to "create programs that will equip and empower kids to reach their full potential in life," according to their foundation's website. They have donated over $2.5 million through their foundation since 2018.
View photos of Adam Thielen and his family as they toured Bank of America Stadium for the first time on Tuesday when Thielen officially signed his contract.