The league announced the move on Wednesday evening.
Gordon has been suspended indefinitely since Sept. 2016, without pay, for multiple violations of the NFL and NFLPA policy and program for substances of abuse.
He is allowed to join the Browns immediately to attend meetings, engage in conditioning work and individual workouts. He will be put on the commissioner's exempt list and is permitted to practice with the team beginning on Monday, Nov. 20. He is eligible, at the team's discretion, to return to active status on Nov. 27 or remain on the commissioner's exempt list for another week before returning to active status.
"As emphasized at today's meeting, everyone - including Josh's teammates and coaches, the Browns' ownership and organization, the Program professionals and all of us at the league office - want him to have every opportunity to resume his career and to be successful in the NFL," Goodell said in a statement.
"Whether that happens, however, at the end of the day will depend on Josh. His commitment to sobriety and to reaching his goals in football and beyond will determine his success. It ultimately is up to Josh."
Gordon, 26, was a Pro Bowl and All-Pro selection in 2013. He had 1,646 yards and nine touchdowns on 87 receptions that season. He had 805 yards and five scores on 50 catches in 2012. Gordon only played five games in 2014 before getting shelved with suspensions.
"We've been informed of the league's decision to reinstate Josh," Browns executive vice president of football operations Sashi Brown said in a team statement.
"The personal well-being of all our players is of the utmost importance to us. We respect and commend Josh for taking the steps necessary to have the opportunity to return to the league. Josh will be in our building in the coming days and we look forward to having him back and sitting with him to discuss his future on our team."
The Browns (0-8) face the Cincinnati Bengals on Sunday, Nov. 26 and the Los Angeles Chargers on Sunday, Dec. 3.