Gordon will be allowed to begin COVID-19 testing Friday, according to the league. If he tests negative for the coronavirus, he could join the Seahawks on Dec. 9.
Gordon can then take part in team meetings, individual workouts and strength and conditioning drills, but he will not be permitted to practice, travel with the club or attend games until Dec. 21. He will be eligible to play in Weeks 16 and 17.
In a post on social media, Gordon said he was "thankful" for his conditional reinstatement.
The NFL announced Gordon's previous suspension the day after the Seahawks' Week 15 game last season, meaning he will have effectively served a one-year ban.
He was suspended indefinitely last December for violating the league's policies on performance-enhancing substances and substances of abuse. It was Gordon's sixth suspension since the 2013 campaign and his fifth for some form of substance abuse.
The 29-year-old Gordon will add more firepower to the Seahawks' wide receiver group. D.K. Metcalf currently leads the league in receiving yards (1,039), while Tyler Lockett and David Moore have held prominent roles in Seattle's offense.
"He's an amazing receiver, a guy who was great last year for us, made some great plays," Seahawks quarterback Russell Wilson said of Gordon on Thursday. "Obviously, he's been a great player over his years and all that. But I think more than anything else, it's a testament hopefully to his growth in life.
"You always want to see people overcome challenges and everything else."
Gordon caught seven passes for 139 yards in five games last season with the Seahawks, who claimed the former Pro Bowl and All-Pro wideout after he was released off injured reserve by the New England Patriots in November 2019. He re-signed with the Seahawks on a one-year deal in September.
Gordon has played only 63 games since the Cleveland Browns selected him in the 2012 supplemental draft. He has recorded 247 receptions for 4,252 yards and 20 touchdowns in his NFL career.