LeBron James Teases Polymarket Partnership

James initially posted a 14-second clip to X and Instagram on Saturday, September 5, showing him entering a stylized Polymarket office before the company's logo and the words "COMING SOON:" appear on screen.

Polymarket reposted the video less than an hour later, replying 'thanks for swinging by our HQ' with a goat emoji.

James' original post was taken down from his personal X page. On Sept. 8, James posted a new 58-second video with an updated caption, indicating it was "in partnership with Polymarket." Polymarket reposted that message, and it remains pinned to their page.

The posts land weeks after James' decision to sign with the 76ers, wrong-footing prediction market traders. Before the move was announced, contracts on Kalshi had the 76ers at around 9% to land James, compared with roughly 45% for the Miami Heat.

Front Office Sports estimated roughly $226 million traded on Kalshi and more than $43 million on Polymarket's international platform tied to the decision, with sports business writer Sam McQuillan's "Cap Space" newsletter putting the combined total above $273 million, more volume than any individual NBA game has generated on these platforms. James ultimately signed a two-year, $8 million contract with a player option.

Neither James nor Polymarket has detailed the exact nature of the arrangement beyond the word 'partnership' in the caption. It remains unclear whether this amounts to a straightforward advertising campaign or a more substantial ambassador, investor, or sponsorship relationship.

Polymarket did not respond to a request for comment from The Block at the time of its report. The confirmed football focus suggests the campaign will target NFL season betting content rather than the NBA, where James remains an active player, thereby avoiding a direct conflict between his playing career and the platform he now fronts.

The posts also mark the first public reveal of a formal relationship between James and Polymarket; Polymarket's own reply, posted within an hour of James's video, is the platform's only public comment on the arrangement so far. Neither side has said whether the deal includes an equity or investor component beyond the advertising campaign both have acknowledged.

A James-Polymarket tie-up would mark one of the highest-profile athlete endorsements yet for a prediction market operator, coming as Kalshi and Polymarket continue to expand aggressively into sports contracts, even as combined volume on the two platforms fell 15% in August, marking its first monthly decline in a year.

It also continues a broader shift of star-athlete endorsement dollars away from traditional regulated sportsbooks like DraftKings toward prediction-market platforms operating under a different regulatory framework.