According to Ian Rapoport of NFL Network, the deal is worth $56 million.
Linebacker Khalil Mack and quarterback Derek Carr were the obvious prizes in the Raiders' impressive 2014 NFL draft class, but Jackson has fared well since Oakland grabbed him with a third-round pick that year. He quickly became a starter in his first season, and he has started all 32 games over the past two years.
Although he moved from left guard to right guard to accommodate the addition of Kelechi Osemele, he remained an effective part of one of the NFL's top offensive lines.
In March, Scott Bair of NBC Sports indicated Oakland's interest in signing Jackson before he became a free agent, noting "teams love him."
General manager Reggie McKenzie later explained the need to lock Jackson down.
"We're always trying to make sure we keep our good players," McKenzie said, per Alex Marvez of Sporting News. "We targeted Derek from the outset. We're going to try and get talking to him and also Gabe."
Oakland first agreed to a five-year, $125 million for Carr before quickly moving to Jackson.
The 25-year-old will now remain in Oakland to help keep one of the NFL's most talented young rosters intact.