"I spoke to (team owner) Mark Davis after the game, and Mark let me know that he's not going to be bringing me back," Del Rio told reporters at his post-game press conference.
"He told me he loved me and appreciated all that I did to kind of get this program going in the right direction, but that he felt the need to change."
Davis later issued a press release thanking Del Rio for his work with the club.
"We appreciate Jack's effort in building the foundation of this team for the future," Davis said.
Last year the Raiders reached the playoffs for the first time in more than a decade. They opened their 2017 campaign with two wins, but they slumped late, losing their last four games.
Del Rio, who received a four-year contract extension from the Raiders in February, posted an 18-13 mark with the franchise, going 7-9 and 12-4 his first two seasons.