The Los Angeles Clippers game against the Denver Nuggets was followed by the Boston Celtics-Toronto Raptors match.
Every player across the teams appeared to kneel during the anthem.
Players stood in previous years but NBA Commissioner said before the season resumed that the league wouldn’t enforce a policy that mandated standing during the anthem.
Critics said the players should have stood to mark the anniversary of 9/11.
“Rough look for NBA players to kneel for the national anthem on the anniversary of 9/11,” Clay Travis of Outkick wrote on Twitter.
“You kneel during the national anthem on September 11th? Disgraceful,” another user told the Celtics.
Raptors and Celtics players also knelt during the Canadian anthem. The Raptors are the only NBA team that’s based in Canada.
Representatives for the four teams didn’t respond to requests for comment.
The NBA Player’s Association didn’t respond to a request for comment. The NBA couldn’t be reached for comment.
The NBA’s season restart came after the association and the league reached an agreement on efforts to fight against what they described as racial injustice.
Courts were painted with the words “Black Lives Matter” and players could choose from one of dozens of slogans like “Equality” for the back of their jerseys.
Some players felt the efforts weren’t enough and refused to play late last month following the police shooting of Jacob Blake, a 29-year-old sexual assault suspect who resisted arrest in Kenosha, Wisconsin.
Players ultimately agreed to keep playing, with the league and the player’s association announcing they would take additional steps in the quest for so-called social justice.
NBA ratings are down this year and the league has received criticism over allegations of injecting politics from top Republicans, including President Donald Trump.
“They’ve become like a political organization, and that’s not a good thing,” he told reporters in Washington last month.