MLB’s Polymarket Exclusivity Tested as Five Teams Partner With Kalshi

Nearly a quarter of MLB's 30 clubs now have a branding partnership with a prediction markets operator, and the exclusivity MLB thought it had sold is looking increasingly theoretical.

On Tuesday, Kalshi announced multi-year branding partnerships with five teams.^[1] 

The Los Angeles Dodgers, Boston Red Sox, Atlanta Braves, San Diego Padres and San Francisco Giants. The deals bring the total to seven MLB clubs partnered with a prediction market operator, following the Mets' partnership with Novig and the Yankees' deal with Polymarket earlier this year. 

The activations start immediately, with signage, social content and fan promotions rolling out at team venues, and the Dodgers going as far as renaming a stadium bar the Kalshi 435 Club.

The problem is that MLB itself is supposed to be locked into someone else already. 

Ahead of this season, Polymarket struck a deal to become the league's exclusive prediction markets exchange partner, shortly after MLB signed a memorandum of understanding with the CFTC on a regulatory framework for the category.

That exclusivity was framed at league level. It clearly wasn't binding on the clubs themselves, and five of them have now walked straight past it to sign with a direct competitor.

MLB hasn't tried to explain the gap. The league issued no statement on the Kalshi deals, and of the five teams, only the Red Sox even acknowledged the news publicly, posting a single emoji in reply on social media.

That silence is doing a lot of work. Either the league-level exclusivity was never as watertight as the Polymarket announcement implied, or MLB is choosing not to enforce it against its own franchises, both of which are more interesting stories than the deal itself.

The California problem sitting underneath it

Three of the five new Kalshi partners, the Dodgers, Padres and Giants, are based in California, a state where sports wagering remains illegal after voters rejected two ballot measures in 2022.

That's not a coincidence worth skipping past. Prediction markets have positioned themselves as federally regulated commodities products rather than state-licensed gambling, which is precisely why they can operate in a state that has twice said no to sportsbooks at the ballot box.

Residents of California, the nation's most populous state, can access sports trading through prediction markets even though sports wagering itself is illegal there. 

For an operator building market share, that's not a side effect, it's the point. Stadium branding in Los Angeles, San Diego and San Francisco puts Kalshi's name in front of exactly the audience that has no legal regulated sportsbook alternative, in the country's largest untapped betting population.

Kalshi says baseball-related trading volume on its platform is up roughly 36 times over the past year. 

Some of that growth is simply the category maturing. But a meaningful share of it is almost certainly Californians finding a federally sanctioned way to do something the state has explicitly refused to legalise twice.

What regulated operators are watching

For licensed sportsbooks, this is the uncomfortable double bind. They can't touch California under current law and pay heavily for market access everywhere they can operate. 

Kalshi and Polymarket are securing exactly the stadium real estate and team affinity that regulated brands spent a decade building, without a state license, an access fee, or in Massachusetts's case, even a functioning product, given Kalshi's sports contracts there remain blocked pending a state Supreme Judicial Court ruling tied to the attorney general's lawsuit.

That squeeze has been building for months, with Genius Sports and Sportradar both signing data and integrity deals with Polymarket and Kalshi that hand the exchanges the same credibility infrastructure regulated sportsbooks spent a decade earning. 

The MLB-Polymarket exclusivity was supposed to be the sport's tidy answer to the prediction markets question. Instead, seven clubs are now proving there isn't one clean answer, and the loudest signal is coming from California, where the market that isn't supposed to exist is the one growing fastest.