The person spoke to The Associated Press on condition of anonymity because the deal had not been announced. ESPN.com first reported the agreement, which was reached Wednesday morning.
The 35-year-old Hasselbeck has spent the past 10 years with Seattle, but the Seahawks reached a deal Tuesday with quarterback Tavaris Jackson.
The Titans were looking for a veteran quarterback to help mentor rookie Jake Locker, the No. 8 overall draft pick. Veteran Kerry Collins announced July 7 he was retiring, and Tennessee plans to trade or release Vince Young likely before training camp on Friday.