Marshall's four-game suspension for substance abuse had been lifted Sept. 30. He was activated Saturday afternoon.
Marshall, 26, enjoyed a strong preseason. He led the team in tackles with 31, including 24 solo stops (also a team-high).
Erwin Swiney, a first-year pro out of Nebraska, was placed on waivers to make room for Marshall on the team's active roster.
Swiney played in three of the Packers four games so far in 2003. His most notable moment was an onside kick recovery in the Week 1.