Hundreds of guests gathered at the Grand Del Mar resort in San Diego for the 4:30 p.m. ceremony, according to KFMB-TV, which obtained an invitation.
James, 28, proposed to his longtime girlfriend, 27, at a party on New Year's Eve 2011, and later admitted on Oprah's Next Chapter that he was nervous. "It felt like a finals game."
The couple sent out Save the Date notes in March for the three-day celebration, which the New York Post reports was masterminded by wedding planner Preston Bailey, who also planned the Lord of the Rings-themed $9 million nuptials of Silicon Valley mogul Sean Parker.
Guests were welcomed to the celebration with a barbecue on Friday evening before the afternoon wedding on Saturday, and the festivities are expected to wind up with a farewell brunch on Sunday, according to reports.
Among those at the ceremony at the resort's Capella Chapel were James's teammate Dwayne Wade and girlfriend Gabrielle Union and NBA players Chris Paul and Carmelo Anthony, reports KFMB. Photographers said they spotted Beyoncé and husband Jay-Z but that couldn't be confirmed.
Brinson, who has two sons with James – LeBron Jr., 8, and Bryce, 5 – told Harper's Bazaar in 2010 that she's dreamed of being a bride since the age of 6 and that when she married James, "I want it to be forever."
"A person like myself always needs a great sidekick and a person you can rely on no matter the circumstances. And she's that," James added. "She's got my back and I love her for that."