Both players signed two-year deals.
Walker was one of San Diego's most versatile players on defense in 2013, seeing time at all four linebacker positions in defensive coordinator John Pagano's 3-4 defensive front.
Walker, 27, signed with San Diego in September before the start of the regular season after being released by Arizona last May.
The Kansas State product started six games and played a total of 451 snaps defensively during the regular season, finishing with 36 tackles, three sacks and a forced fumble.
Ghee, 26, played in 23 games during part of four seasons with Cincinnati, totaling 17 tackles and five pass breakups. At 6-0 and 200 pounds, Ghee was a third-round selection by the Bengals in the 2010 draft.