In a statement, the league said that Seattle's last-second touchdown pass should not have been overturned.
"When the players hit the ground in the end zone, the officials determined that both (Seahawks receiver Golden Tate) and (Green Bay safety M.D. Jennings) had possession of the ball. Under the rule for simultaneous catch, the ball belongs to Tate, the offensive player. The result of the play was a touchdown," the NFL's statement said.
The game had gone down to the wire, with the Seahawks trailing and the clock winding down. Quarterback Russell Wilson unleashed a 24-yard Hail Mary pass, and then there was a scramble in the end zone.
The NFL said Tate should have been called for offensive pass interference before the catch, which would have ended the game, but that call was not made and is not reviewable in instant replay.
One referee called a touchdown, while the other said no. The game didn't officially end for another 10 minutes. Both teams went to their locker rooms while the referees conferred. Tate ended up getting credit for the game winner, but even he seemed confused.
"I heard it was a touchdown, and you know, there we go," he said after the game.
The incident may be the impetus to end the lockout of NFL referees. The NFL locked out the officials in June after their contract expired, and the two sides were unable to reach a new collective bargaining agreement. The season opened with replacements, most with experience only in lower levels of college football.
ESPN's Ed Werder says the side judge who made the touchdown call, identified as Lance Easley, was among the least experienced of the replacement officials. Easley apparently never officiated above Division III, according to information the league provided.
Three weeks of chaos and controversial calls are taking their toll.
"It was awful," Packers quarterback Aaron Rodgers said to reporters after the game. "Just look at the replay."
The Associated Press contributed to this report.