Miami Dolphins wide receiver Kenny Stills, tight end Julius Thomas and safety Michael Thomas took a knee during the national anthem prior to Sunday's game against the New Orleans Saints at Wembley Stadium in London.
The three players then stood for the British anthem.
The Saints players knelt together as a team before the national anthem and then stood together during the playing of the anthem, performed by Darius Rucker, in a planned show of unity. Many players and coaches had their arms interlocked or their hands on shoulders.
Thomas started kneeling last Sunday, two days after President Donald Trump said during a political rally in Huntsville, Ala., that NFL owners should fire the players who knelt during the anthem.
"We're proud of our country. We respect our flag," Trump said to loud applause at the campaign event. "Wouldn't you love to see one of these NFL owners, when somebody disrespects our flag, to say, 'Get that son of a bitch off the field right now. Out. He's fired! He's fired!'"
Trump's position unified more players kneeling during the anthem to protest racial injustice as demonstrations were organized across the NFL last Sunday.
Trump on Saturday renewed his criticism of players who have refused to stand during the pregame ceremony.
"Very important that NFL players STAND tomorrow, and always, for the playing of our National Anthem," Trump tweeted Saturday night. "Respect our Flag and our Country!"
Quarterback Drew Brees announced the Saints' plans earlier in the week.
"I don't blame the guys for feeling like they needed to do something as a reaction," Brees said. "Unfortunately I think he put all athletes, all black athletes, minority athletes, he put 'em in a corner and forced them to take action."