The picture displays the commander-in-chief's face with the words "Believe in something. Even if it means sacrificing everything. Just do it."
Trump's eldest son wrote a caption below the post that says, "There, fixed it for you. #maga (make America great again)."
The "believe in something" message is part of a new ad campaign Nike launched with Kaepernick on Tuesday. A commercial is scheduled to air Sunday during the opening week of the 2018 NFL season.
Nike posted the commercial on its official Twitter page on Tuesday.
Kaepernick, a former quarterback with the San Francisco 49ers, has been out of the league for nearly two years, since he began kneeling during the national anthem at NFL games to protest social injustice and police brutality against minorities.
According to The Associated Press, Kaepernick previously had a deal with Nike that was about to expire, but the two sides worked to renegotiate a multiyear contract, which made him one of the faces of Nike's 30th anniversary "Just Do It" campaign.
After news of Kaepernick's new deal with Nike was announced, the company's stock fell by 2 percent.