He will begin on the practice squad, and if he's ready ahead of the Lions' NFC championship game against the San Francisco 49ers, the 33-year-old could be elevated to the active roster.
Ertz was most recently with the Arizona Cardinals, but he asked for his release this season and hoped to join a contender.
"Brock, we’ll see," Campbell said after the game. "Doesn’t look real good for next week, but we’ll see.”
Some of the logic behind bringing in Ertz, a three-time Pro Bowler who won a Super Bowl with the Philadelphia Eagles, is that he's somewhat familiar with what the Lions do.
The former Cardinal played under current Lions tight ends coach Steve Heiden last season when Heiden was coaching tight ends in Arizona. Ertz has spent his 12-year career with the Eagles (2013-2021) and Cardinals (2021-2023). He has recorded 709 catches for 7,434 yards and 46 touchdowns.