Vick can immediately participate in preseason practices, workouts and meetings and can play in the final two preseason games — if he can find a team that will sign him. A number of teams have already said they would not.
"Needless to say, your margin for error is extremely limited," Goodell said in a letter to Vick. "I urge you to take full advantage of the resources available to support you and to dedicate yourself to rebuilding your life and your career. If you do this, the NFL will support you."
Goodell suspended Vick indefinitely in August 2007 after the former Atlanta Falcons quarterback admitted bankrolling the "Bad Newz Kennels" dogfighting operation. Goodell said then that Vick must show remorse and signs that he has changed before he would consider reinstating him.
Once the season begins, Vick may participate in all team activities except games, and Goodell said he would consider Vick for full reinstatement by Week 6 (Oct. 18-19).
Goodell called a news conference for late Monday afternoon.
"I would like to express my sincere gratitude and appreciation to commissioner Goodell for allowing me to be readmitted to the National Football League," Vick said through agent Joel Segal. "I fully understand that playing football in the NFL is a privilege, not a right, and I am truly thankful for the opportunity I have been given.
"As you can imagine, the last two years have given me time to re-evaluate my life, mature as an individual and fully understand the terrible mistakes I have made in the past and what type of life I must lead moving forward.
"Again, I want to thank the commissioner for the chance to return to the game I love and the opportunity to become an example of positive change."
The announcement came after a busy first week of freedom for Vick, who met with union leaders and Goodell on consecutive days last week. His 23-month federal sentence ended when an electronic monitor was removed from his ankle early on July 20 at his home in Hampton, Va.
He met with DeMaurice Smith, executive director of the NFL Players Association, last Tuesday and, on Wednesday, he sat down with Goodell at a security firm in Allendale, N.J.
But his issues are far from over. Already, the owners of the New York Giants and New York Jets said they have no interest in the 29-year-old quarterback, who once was the league's highest-paid player.
AP Sports Writer Hank Kurz in Richmond, Va., contributed to this story.