Trufant became a free agent after the Falcons released him with three years and $35.25 million remaining on his contract. The move saved Atlanta about $5 million in salary-cap space.
Trufant, who turns 30 in September, was selected in the first round of the 2013 NFL Draft out of Washington. He was named to the PFWA's All-Rookie Team in 2013 and was selected to the Pro Bowl in 2015.
Injuries derailed Trufant's time with the Falcons, including a broken forearm that limited the star defensive back to nine games last season. Before the season-ending injury, he notched a career-best four interceptions.
In seven seasons with the Falcons, Trufant started 97 games and tallied 329 total tackles, 13 interceptions, 79 passes defensed, five sacks, three forced fumbles and seven fumble recoveries.
With Trufant joining the Lions, the franchise will face the question of whether to have him replace star cornerback Darius Slay, who has been a candidate to be traded since last season. Detroit also could opt to keep Slay and pair him with Trufant in 2020.
Once the agreement was reported, Slay congratulated Trufant on social media, while also saying, "Hope that speeds up my trade process!!"
Slay recorded 46 total tackles, two interceptions and 13 passes defensed in 14 regular-season games in 2019.