MLB’s Polymarket ‘Integrity’ Deal Has Limitations

MLB announced a partnership with Polymarket on Thursday that includes integrity monitoring, data sharing and the right to use intellectual property. But the bulk of the agreement doesn’t cover that Polymarket.

It’s focused on Polymarket’s yet to be fully launched U.S. prediction market exchange, rather than Polymarket’s separate crypto-based international exchange, for which the company is widely known.

While MLB has touted the agreement as necessary to enhance integrity standards in prediction markets, giving it the right to “restrict markets that present an integrity risk,” this provision has limited meaning right now. Polymarket’s much-larger international exchange is not subject to the same terms of the deal. 
 
To get a sense of how tiny Polymarket’s U.S. product is currently, its notional betting volume in 2026 is about $700 million, compared with about $20 billion for the company’s international exchange. Kalshi, a Polymarket competitor, recorded $3 billion in notional volume last week alone (Kalshi has one exchange, which is U.S.-based but also takes bets in some other countries).

Notional volume on Polymarket U.S. actually decreased from January to February.

Polymarket’s branding, which MLB will use, is the same for its U.S. and international units. The international exchange is where bets on military strikes are listed, which has drawn the ire of U.S. lawmakers. It also facilitated bets on whether sex toys would be thrown on WNBA courts last year. And the product does not ask users to provide personal identification before placing bets—a requirement for U.S.-based exchanges meant to guard against bad actors.

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