King, who last played in the NFL in 2004/2005, rejoins his old Tampa Bay coach Rod Marinelli. Marinelli was familar with King from his days as the starting quarterback in Tampa. King received a tryout last year during the bye week with the Lions but was not signed at the time. He was released by Cardinals head coach Dennis Green last year, but was never picked up.
In three games for Arizona in 2004, King completed 47 of his 84 passes for 502 yards, garnering one touchdown and tossing four interceptions.
"It went very well, extremely well," King told the Ft Lauderdale Sun-Sentinel of his workout for the Lions. "In fact, I signed with them. I have to go back up there on Sunday. I'm very excited about the opportunity."
King will likely have to fight for a roster spot for the 3rd string, veteran backup role. Detroit is still thought to be in the mix for several free agent quarterbacks including San Diego's Drew Brees, Tampa's Brian Griese and New York's Chad Pennington.