Witten has decided to end his NFL playing career, ESPN's Todd Archer reports.
Witten totaled 13 receptions (on 17 targets) for 69 yards and two touchdowns in 16 games during the 2020 season, though he was not targeted in the Raiders' Week 17 finale against the Broncos.
Witten caught two of five targets for 12 yards in Saturday's 26-25 loss to the Dolphins.
Witten failed to haul in his only target during Sunday's 31-28 win over the Jets.
Witten caught a one-yard touchdown pass on his only target in Sunday's 35-31 loss to the Chiefs.
Witten caught two passes on as many targets for 21 yards in Sunday's 16-6 win over the Browns.
Witten caught both of his targets for six yards in Sunday's 40-32 win over the Chiefs.
Witten turned his only target into a two-yard reception during the Raiders' Week 1 win over the Panthers on Sunday.
Witten will sign a one-year deal with the Raiders, Adam Schefter of ESPN reports.
Witten isn't expected to re-sign with the Cowboys, Clarence E. Hill Jr. of the Fort Worth Star-Telegram reports.