The deal is expected to end Ryan Fitzpatrick's run with the Titans as Jake Locker's backup after one season.
Whitehurst visited Saint Thomas Sports Park on Thursday, but he and the Titans already had some tight connections.
Whitehurst, 31, backed up Philip Rivers last season in San Diego when Titans coach Ken Whisenhunt was Chargers offensive coordinator, and new Titans offensive coordinator Jason Michael was San Diego's tight ends coach last season.
The contract includes $4 million in base salary with $2 million fully guaranteed and $4 million in incentives, according to sources familiar with the deal.
Whitehurst was a third-round pick of the Chargers in 2006, but he does not have a great deal of NFL experience.
He spent his first four seasons in San Diego (2006-09) but didn't accumulate any stats. The Chargers traded him to the Seahawks in 2010, and he returned to the Chargers in 2012.
He played in two games last season but did not throw a pass. In his career he has completed 84 of 155 passes for 805 yards and three touchdowns — all of those yards when he played for Seahawks from 2010-11.
The Chargers were interested in re-signing Whitehurst, but his opportunity with the Titans could be better as Locker has battled injuries in his two seasons as the starter.
Fitzpatrick backed up Locker last season, but he's scheduled to collect a $500,000 roster bonus within the next week and has a scheduled base salary of $2.75 million for 2014.
Fitzpatrick started nine games last season in place of an injured Locker and completed 217 of 350 passes for 14 touchdowns and 12 interceptions. Some of his turnovers came at highly inopportune times.
Fitzpatrick, 31, signed a two-year deal with the Titans last offseason to replace Matt Hasselbeck. He made $1.5 million last season after collecting a $1.75 million signing bonus.
The Titans also have quarterback Tyler Wilson under contract. Rusty Smith became a free agent on Tuesday.