LeBron James of the Cleveland Cavaliers wore a shirt that said, "I Can't Breathe," Garner's infamous last words, during pregame warm-ups before facing the Brooklyn Nets Monday night in New York.
Garner uttered that sentence before he died this summer, after a white police officer put him in an apparent chokehold.
Janaye Ingram of the National Action Network told ABC News today the show of support from famous athletes is "definitely good for the movement."
"A lot of our society is very celebrity-focused," she said. "These athletes recognize that had it not been for their talent that led them to the sports arenas, it could have been them that faced a similar situation."
"They have a platform that is unlike any other platform," Ingram added. "It raises the level of consciousness."
Chicago Bulls guard Derrick Rose was spotted in a similar shirt to James' during warm-ups this weekend. The NFL is also getting in on the action: several football players, including Detroit Lions running back Reggie Bush and Cleveland Browns cornerback Johnson Bademosi, have written "I Can't Breathe" on their clothing.
St. Louis Rams offensive linesman Davin Joseph even had the message scrawled on his cleats.
The Rams also staged a protest Nov. 30, a week after a grand jury voted not to indict the white police officer who shot and killed 18-year-old Michael Brown this summer in Ferguson, Missouri. Five players walked onto the field before an NFL game against the Oakland Raiders with their hands in the air, the same "hands up, don't shoot" gesture adopted by protesters.
Athletes having been showing support for Brown, who was unarmed, for months, including former NBA star Allen Iverson, seen here wearing a "Mike Brown" T-shirt, and Ben McLemore of the Sacramento Kings, who wrote "RIP Mike Brown" on his sneakers:
Kings G Ben McLemore - a St. Louis native - wrote "RIP Mike Brown" on his sneakers (Rocky Widner/Getty) pic.twitter.com/JrkKpVAjP5— Ben Golliver (@BenGolliver) December 1, 2014
It's not the first time athletes have rallied behind a cause. In 2012, many professional sports players protested the killing of Travyon Martin, the 17-year-old in Florida who was shot dead by a neighborhood watchman. They posted photos of themselves wearing black hoodies, which Martin was wearing when he was killed, on social media.