Prediction markets just had their biggest month ever. Kalshi and Polymarket processed nearly $45 billion in combined trading volume during June, a 75% jump from the prior month that cements the sector as one of the fastest-growing corners of the financial landscape.

To put that number in perspective, combined monthly volumes for the two platforms sat below $5 billion as recently as September 2025. Nine months later, they’ve grown roughly ninefold.

Kalshi is running away with market share

Of the two platforms, Kalshi is doing most of the heavy lifting. The US-regulated exchange processed approximately $22.6 billion in notional volume in June, significantly outpacing Polymarket and commanding about 74% of weekly market share in recent tallies.

The secret ingredient is not exactly a secret: sports betting. An estimated 80% of Kalshi’s trading volume comes from sports markets, turning what was originally pitched as a platform for hedging real-world events into something that looks a lot more like a sportsbook with extra steps.

Polymarket takes a different approach. Sports betting accounts for a smaller share of its volume, somewhere in the range of 39% to 45%, with the platform maintaining broader interest in political outcomes and crypto-adjacent markets.

Weekly trading volumes across both platforms recently hit $13.9 billion. The trajectory from under $5 billion monthly in September to roughly $24 billion in April to $45 billion in June suggests the growth is accelerating, not plateauing.

Big valuations, bigger expectations

The venture capital world has noticed. Kalshi closed a funding round in May 2026 that valued the company at $22 billion, with some projections suggesting a potential path to $40 billion.

Polymarket’s valuation sits around $15 billion, built on blockchain infrastructure. Neither platform has prominently tied any crypto tokens to their core operations, despite Polymarket being built on blockchain rails.

What this means for investors and traders

The dominance of sports betting also creates concentration risk. If regulators decide to draw sharper lines between prediction markets and traditional sports gambling, Kalshi’s volume engine could face headwinds. Regulatory scrutiny around prediction markets has been increasing, particularly regarding potential insider trading on geopolitical and political events.

For the competitive landscape, the divergence between Kalshi and Polymarket is worth watching. Kalshi’s bet on sports volume is paying off spectacularly right now, but Polymarket’s more diversified approach could prove more resilient if regulatory winds shift. A platform that derives 80% of its volume from one category is inherently more vulnerable to category-specific disruption than one with a broader base.