World Cup 2026 Sends Prediction Market Trading to Record Highs, With Kalshi Topping $31 Billion in June

The Numbers

Kalshi recorded more than $31 billion in notional trading volume during June, a 70%-plus jump from May's $17.9 billion, according to user-collected data on Dune Analytics. The platform has logged over $1 billion in daily volume on most days since the tournament kicked off June 11.

Polymarket's international exchange set a new monthly record as well, with notional trading exceeding $10.8 billion in June. That reverses a slide in April and May when volume had been falling. Polymarket's U.S. platform added another $3.5 billion, up from $1.77 billion the prior month, according to CNBC.

A newer player also made noise. Rothera, a joint venture between Susquehanna International Group and Robinhood, launched in June when Robinhood began routing certain World Cup contracts through the platform. It pulled in $2 billion in notional volume in its first month and already accounts for 7% of U.S. prediction market volume, per Bank of America.

What's Actually Being Traded

More than $64 million on Kalshi and $122 million on Polymarket has been traded on whether the United States wins the tournament. The odds are not encouraging for American optimists: Kalshi has the U.S. at 4.3%, Polymarket at 3%.

Team USA is set to face Belgium in the round of 16 on Monday night. Whatever happens, the action has already been substantial.

Open interest, the total value of active unsettled contracts, reflects the same enthusiasm. Kalshi's open interest has climbed above $1 billion. Polymarket's international platform sits just under $400 million, elevated but roughly in line with recent months, according to CNBC.

The Pressure Test

Asaf Meir, CEO of Solidus Labs, a market integrity firm that partners with Kalshi, put the stakes plainly: "The World Cup is such a huge pressure test to see whether indeed prediction markets are able to deliver their word on maintaining a level playing field for all investors for a long period of time in a sustained high-volume environment."

Meir said regulators and institutional investors are watching and asking basic questions: is the infrastructure safe, is it mature, does it have enough liquidity? Those are fair questions. Prediction markets have spent the past few years arguing they deserve to operate more like financial exchanges. Volume records are evidence, but they're not the whole argument.

Platforms leaned hard into the marketing opportunity. Polymarket launched a competition offering up to $2 million to whoever assembles a perfect knockout bracket. Kalshi advertised the ability to "Trade the World Cup" directly in its Apple App Store listing.

Concerns About Market Structure

Critics of prediction markets have a reasonable point: high volume in a sports context does not automatically prove that these platforms function well as price-discovery tools for political or economic events. The worry is that retail traders chasing World Cup action could be operating in a market with structural advantages for sophisticated algorithmic traders, and that record volume in a high-emotion sports environment might paper over liquidity and integrity problems that would only surface under different conditions.

That concern isn't settled by a big June number. Meir's own framing acknowledged as much: sustaining a level playing field over a "long period" in a "sustained high-volume environment" is the test, and one month of World Cup trading is not a completed verdict.

Where Things Stand as of July 4

The World Cup knockout rounds are ongoing. The regulatory conversation around prediction markets—specifically whether the CFTC will expand or restrict what event contracts can cover—has not produced a final ruling. The record June volumes give platforms concrete data to take into those conversations, but whether regulators treat that data as reassuring or as a reason for tighter oversight remains an open question.

Robinhood's partnership through Rothera is the structural development most worth watching going forward: if a major retail brokerage can funnel prediction market volume at scale, the industry's growth trajectory shifts significantly, and so does the regulatory calculus.