Wilcox, 26, spent his first four seasons with the Cowboys, who drafted him in the third round in 2013. Wilcox was a full-time starter in 2014-15 and started four games while playing in all 16 last season.
Per previous reports, Wilcox had also planned to visit the Seahawks before the Buccaneers convinced him to agree to terms.
Wilcox has five career interceptions, two forced fumbles and three fumble recoveries. He’s started 38 of 58 career games.
The Cowboys previously lost safety Barry Church in free agency to the Jaguars.