Since the tournament kicked off on June 11, the platform has sustained daily volumes above $1 billion. Meanwhile, Polymarket's international exchange posted a historic monthly high with over $10.8 billion in notional trading, breaking the downward trend of April and May. On its U.S.-facing platform, Polymarket saw about $3.5 billion in notional volume for the month, more than doubling May's $1.77 billion.
On Monday night, Team USA will face Belgium in the round of 16. Wagers placed on the U.S. winning the entire tournament have reached $64 million on Kalshi and $122 million on Polymarket, though the platforms give the Americans only a 4.3% and 3% chance, respectively. The World Cup has also given a boost to Rothera, a platform created by a partnership between Susquehanna International Group and Robinhood.
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Launched in June, Rothera began receiving certain World Cup contracts routed from Robinhood's brokerage. In its first month, Rothera handled $2 billion in notional trading volume and now commands 7% of the U.S. prediction market, according to Bank of America.
Every major platform used the World Cup to attract users. Polymarket offered a $2 million prize for anyone who could submit a flawless knockout round bracket, while Kalshi promoted its app on the Apple App Store with the tagline "Trade the World Cup" in the app's name.
Increased open interest - the value of all active unsettled contracts - also points to World Cup fervor. Kalshi's open interest now exceeds $1 billion, while Polymarket's sits just under $400 million, roughly where its international platform has hovered in recent months. Sports dominated event contract exchanges last month, but how these platforms handled the volume surge could indicate their readiness for other contract types in the future.
Asaf Meir, CEO of market integrity firm Solidus Labs - which partners with Kalshi - said, "Is it safe enough? Is it mature enough? Does it have enough volume? 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."
The tournament, which began on June 11 and runs through mid-July, has drawn record global attention. With matches scheduled almost daily, prediction exchanges have experienced sustained engagement, testing their infrastructure under unprecedented load. The round of 16 matchup between Team USA and Belgium later this week is expected to drive further activity as bettors adjust positions.
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