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.
