The deal comes with a guaranteed $52.27 million for Mendoza, and also includes a fifth-year option.
He led Indiana to their first national championship and a perfect 16-0 record in 2025, completing 72% of his passes. Mendoza also threw for 3,535 yards, 41 touchdowns, and only six interceptions in what was his only year with the Hoosiers.
His performance led to him being awarded the Heisman Trophy, and was a name many were looking out for during the NFL draft.
While Mendoza is expected to be the long-term face of the Raiders, the AFC West team signed Kirk Cousins in the offseason as well, with the veteran quarterback likely to be the starter for their opening game of the season.
It was reported that the Raiders and Mendoza had a disagreement on his signing bonus, but the team did not provide any details on Thursday in their press release.
In his first two collegiate years, Mendoza suited up for Cal, throwing 4,712 combined yards along with 30 touchdowns and 16 interceptions in his 20 games with the Golden Bears.