The ex-49ers star unveiled the ad on Twitter, which says, "Believe in something. Even if it means sacrificing everything. #JustDoIt"
The ad commemorates the 30th anniversary of Nike's "Just Do It" campaign, and Kaepernick -- who spearheaded a protest movement against social injustice by kneeling during the national anthem -- has been out of job for more than a year. But this latest ad marks a new multi-year deal with the sports apparel giant.
"Pretty powerful when I saw that," Nike customer Marisa Smith said
Nike is already facing criticism, with many calling for a boycott. Social media video showed someone burning a pair of Nike shoes, while others questioned Nike's true motives.
"You've got children in sweatshops making your shoes all over the world, and then you got LeBron putting them because they say 'equality,'" Carlos Rodriguez said. "So a bunch of people here will buy them. They'll make a bunch of money. But is equality what they're really striving for? Or are they just really trying to sell some sneakers?"
Country singer John Rich of Big & Rich criticized Nike, posting a picture of cut up Nike socks.
Rich tweeted on Monday night that a member of his crew cut the trademark swoosh off his socks and that he was also planning to burn them.
In a series of tweets that continued Tuesday, Rich, who was also on "The Celebrity Apprentice," said he supported the right to protest, but that Nike lost his support when they endorsed Kaepernick.
President Donald Trump, a frequent critic of protesting NFL players, did not weigh in Tuesday morning even though he has loudly urged the league to suspend or fire players who demonstrate during the anthem, repeatedly diving into what has developed into one of the most contentious debates in the sports world.
Kaepernick's attorney Mark Geragos announced the endorsement deal on Twitter, calling Kaepernick an "All American Icon."
Kaepernick already had a deal with Nike that was set to expire, but it was renegotiated into a multiyear deal to make him one of the faces of Nike's 30th anniversary "Just Do It" campaign, according to a person familiar with the contract. The person spoke to The Associated Press on condition of anonymity because Nike hasn't officially announced the contract.
The person said Nike will feature Kaepernick on several platforms, including billboards, television commercials and online ads. Nike also will create an apparel line for Kaepernick and contribute to his Know Your Rights charity, the person said. The deal puts Kaepernick in the top bracket of NFL players with Nike.
Nike also provides all NFL teams with game-day uniforms and sideline apparel, a partnership that was extended in March to run through 2028.
Last week, Kaepernick scored a legal victory in his grievance against the NFL and its 32 teams when an arbitrator allowed his case to continue to trial. The quarterback claims that owners conspired to keep him out of the league because of his protests of social injustice.
Kaepernick contends the owners violated their collective bargaining agreement with players by conspiring to keep him off teams. His case hinges on whether owners worked together rather than decided individually to not sign Kaepernick.
A similar grievance is still pending by former 49ers teammate Eric Reid, a Pro Bowl safety who joined in the protests.
On Friday night, Kaepernick and Reid, also now out of the league, were each given huge ovations when they were introduced and shown on the big screen during a match between Serena and Venus Williams at the U.S. Open.
Meanwhile, the league and players union still haven't resolved whether players will be punished this season if they choose to kneel or demonstrate during the national anthem. Owners approved a policy requiring players to stand if they are on the sideline during "The Star-Spangled Banner," allowing them to stay off the field if they wish.
But the league and union put that on hold after the Miami Dolphins faced backlash for classifying the protests as conduct potentially detrimental to the team - putting players at risk of fines or suspensions.
(The Associated Press contributed to this report)
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