Polymarket volume surges 300% during World Cup, Kalshi hits $1B open interest

The 2026 FIFA World Cup is doing for prediction markets what March Madness does for office pools, except the stakes are measured in billions. Polymarket’s soccer category blew past $2 billion in trading volume within the first ten days of the tournament, a 300% jump compared to the equivalent period before kickoff.

Kalshi, meanwhile, crossed a milestone of its own. The platform’s aggregated open interest hit $1.16 billion last week, the first time it has ever breached the billion-dollar threshold, representing a 350% increase year-to-date.

The numbers behind the frenzy

Polymarket’s daily trading volume in the soccer category jumped from roughly $53 million to $220 million during the tournament’s opening stretch. Sports-related daily trade volumes on the platform reached over $300 million at peak, doubling from pre-tournament levels.

The flagship World Cup winner market on Polymarket alone has accumulated a lifetime trading volume between $2 billion and $3 billion. That is a single market on a single platform, handling more volume than many mid-cap crypto tokens see in a month.

Combined turnover across both Polymarket and Kalshi in World Cup-related markets has now surpassed $5 billion.

Polymarket’s overall open interest has remained relatively stable even as volume has spiked, suggesting heavy turnover with traders rotating in and out of positions. Kalshi’s open interest, by contrast, has been climbing steadily, which points to a stickier, more institutional user base holding positions longer.

Why this World Cup is different

The FIFA World Cup kicked off on June 11. Kalshi reportedly closed a $1 billion funding round earlier in 2026, giving it the war chest to compete not just with Polymarket but with traditional sportsbooks and financial exchanges.

Polymarket’s on-chain settlement model means every bet resolves transparently, and the platform has become a de facto data source for real-time probability estimates on everything from geopolitics to penalty shootouts.

What this means for investors

Kalshi operates under CFTC oversight in the US, which gives it a compliance moat but also subjects it to shifting political winds. Polymarket, structured for non-US users, faces its own jurisdictional complexities.

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