The defensive tackle recently served a two-month jail stint on a probation violation on gun-related charges.
He's the third player suspended by commissioner Roger Goodell in little more than a month for off-field behavior. In April, Goodell suspended Tennessee Titans defensive back Adam "Pacman" Jones for the entire 2007 season and Cincinnati Bengals wide receiver Chris Henry for eight games. Jones is appealing his suspension.
Goodell said Johnson's suspension could be reduced to six games if he has no further involvement with law enforcement and undergoes counseling.
After meeting with Goodell upon his release last month, Johnson said he was ready to accept whatever punishment Goodell handed down and that he wants to become the NFL's "Man of the Year," the player honored for being its best citizen.
There was no statement from the league other than the short announcement of the suspension. It said Goodell would review Johnson's status before Oct. 1 to determine whether to reduce his suspension by two games.
Last December, police raided the 300-pound defensive tackle's suburban Chicago home and found six unregistered firearms — a violation of his probation on an earlier gun charge.
That charge stemmed from Johnson's 2005 arrest after a Chicago nightclub valet reported seeing Johnson with a handgun in his SUV. He subsequently pleaded guilty to a misdemeanor charge.
Two days after the raid, Willie B. Posey, Johnson's bodyguard who had been arrested after the raid, was shot and killed in an early-morning fight while he and Johnson were at a Chicago nightclub.
Johnson was suspended by the Bears for one game for being at the club. He played with the team in the Super Bowl.
In March, Johnson began his jail term for violating his probation. Last month, he pleaded guilty to a misdemeanor weapons charge as part of a deal with prosecutors that kept him from serving more time in jail. He was ordered to serve 45 days, which he was able to serve concurrently with the sentence for violating his probation.
Johnson met with Goodell for 90 minutes in New York on May 18.
"I feel like whatever sanction he imposes, I'm man enough to take it and I know that once I get back on the field, that chapter of my life is closed and I can move on with a sense of closure," Johnson said after the meeting.
He called the commissioner "a fair man" and added: "One day I want to be the face of the league for guys who have come through adversity, came through it and ultimately became the Man of the Year in the NFL. That would be a tremendous ending to the story."