He has been a member of the Hamilton Tiger-Cats of the Canadian Football League (CFL), and the New Orleans Saints, Oakland / Las Vegas Raiders, Atlanta Falcons, and San Francisco 49ers of the NFL.

Throughout training camp in 2017, Harris competed to be the starting free safety against Vonn Bell and Rafael Bush after the role was left vacant by the departure of Jairus Byrd.

Head coach Jack Del Rio named Harris the primary backup free safety, behind Karl Joseph, to start the 2017 regular season.

[15] Head coach Jon Gruden names Harris the primary backup strong safety, behind Karl Joseph, to begin the 2018 NFL season.

On December 16, 2018, Harris recorded three solo tackles, deflected two passes, and made his first career interception during a 30–16 loss at the Cincinnati Bengals.

Harris made his first career interception off a pass by Bengals' quarterback Jeff Driskel, that was originally intended for John Ross.

[18] Harris entered training camp slated as a backup safety after the Raiders drafted Johnathan Abram in the first round.

Head coach Jon Gruden retained Harris as the primary backup strong safety, behind Karl Joseph, to start the season.

[19] Harris became the starting free safety in Week 2 after Johnathan Abram was placed on injured reserve after tearing his rotator cuff during the Raiders' season-opening 24–16 victory against the Denver Broncos.

On September 29, 2019, Harris made seven combined tackles (six solo), a pass deflection, and returned his first career interception for a touchdown during a 31–24 win at the Colts.

Harris intercepted a pass attempt by Jacoby Brissett, that was intended for wide receiver Zach Pascal, and returned it for a 30-yard touchdown during the fourth quarter.