Prediction market trading climbed sharply in June as the 2026 FIFA World Cup drove a wave of activity across major platforms. Kalshi recorded more than $31 billion in notional volume for the month, up more than 70% from May’s $17.9 billion, while Polymarket’s international platform reached a record monthly total above $10.8 billion. Polymarket’s U.S. platform also rose to more than $3.5 billion from $1.77 billion in May, and Rothera, a new venture backed by Susquehanna International Group and Robinhood that launched in June, logged $2 billion in trading volume.
The tournament became a major draw for event-contract exchanges, with platforms promoting World Cup-related markets and contests to attract users. Since the competition began on June 11, Kalshi has sustained more than $1 billion in daily volume. Trading tied to the U.S. team’s prospects also drew substantial participation, with more than $64 million traded on Kalshi and $122 million on Polymarket over whether the United States would win the tournament, though both platforms assigned the team relatively low odds. Open interest also remained elevated, topping $1 billion on Kalshi and nearing $400 million on Polymarket’s international platform.
Supporters of the sector say the World Cup has become a test of whether prediction markets can handle intense demand while maintaining orderly trading. Asaf Meir, chief executive of market integrity firm Solidus Labs, said regulators and institutions are watching whether platforms can operate safely and fairly during a sustained period of heavy volume. Kalshi chief executive Tarek Mansour has also argued that insider trading can be easier to identify in prediction markets than in stocks because bets are tied more directly to specific events. He said Kalshi has adopted guardrails including employment verification and whistleblower channels, and pointed to the company’s reporting of unusual trades linked to former Rep. George Santos, who is under investigation by the Justice Department and the Commodity Futures Trading Commission.
Critics and state officials, however, remain unconvinced. Lawmakers in several states have moved to ban, limit or tax prediction markets, arguing that the platforms function like unlicensed sportsbooks while benefiting from federal oversight through the Commodity Futures Trading Commission rather than state gambling rules. Arizona has filed criminal charges against Kalshi, while Nevada and Michigan have pursued bans, and Kentucky and North Carolina have moved to impose new taxes on operators’ fees. The broader dispute has produced mixed court outcomes and raised larger questions about how prediction markets should be regulated as their trading volumes continue to expand.