The Ravens announced the move late Friday night. Spears is expected to take a physical and sign the deal within the next few days.
Although the Super Bowl champions have lost several key players during free agency, they've enhanced their defensive line by signing Chris Canty and Spears, who has 89 starts over his NFL career.
General manager Ozzie Newsome says, "The base of a good defense is to be good along the defensive line. Spears, like Canty, can play multiple positions along the line. He brings a lot of snaps and big game experience to us.''
Spears was drafted in the first round of the 2005 draft by Dallas.