Brady, who played 23 NFL seasons before retiring in 2022, will hold a five per cent stake in the Raiders, who are off to a 2-4 start this season.
The approval at an owners meeting in Atlanta ends an 18-month saga since the first reports of Brady seeking a share of the partnership group that owns the club.
Delays in the deal reportedly included figuring out an exact percentage for Brady and issues around his current role as an NFL television analyst for Fox Sports.
Two months ago, the NFL put some restrictions on Brady's broadcast access because of his possible involvement with the Raiders.
Brady is banned from attending in-person or online broadcast production meetings and is not allowed access to players, coaches or team facilities.
While he is permitted to broadcast Raiders contests, Brady must follow NFL rules banning criticism of other teams or officials.
Brady, 47, spent 20 seasons with the New England Patriots, leading them to six NFL titles, and captured his last crown with Tampa Bay in 2020.
He set NFL career records with 7,753 completions from 12,050 attempts for 89,214 yards and 649 touchdowns.