TLDR
- Combined monthly volume at Kalshi, Polymarket, and Polymarket US fell 14.5% in August to $45.33 billion, the first monthly decline in a year.
- Kalshi recorded $37.17 billion in volume, down 7.3% from July’s $40.1 billion.
- Polymarket and its US platform combined for $8.16 billion, down 36.7% from July’s $12.89 billion.
- The drop follows a World Cup driven surge that pushed volumes higher through June and July.
- Kalshi faces state lawsuits over sports betting while still signing new sports partnerships and issuing its first permanent trading ban.
Prediction market platforms Kalshi and Polymarket saw their combined trading volume fall last month. It was the first month over month drop in a year.
According to data from The Block, combined monthly volume across Kalshi, Polymarket, and Polymarket US fell 14.5% in August. The total came to $45.33 billion, marking the first decline since August 2025.
Kalshi made up the largest share of that volume. The platform recorded $37.17 billion in August, down 7.3% from $40.1 billion in July.
Polymarket and its separate US platform saw a steeper drop. Combined volume fell 36.7% to $8.16 billion, down from $12.89 billion the month before.
Volume Still Higher Than Spring Levels
The August pullback came after a summer spike tied to the World Cup. The tournament ran from June 11 to July 19 and pushed trading activity up across both platforms.
Even with the decline, August volume stayed well above earlier levels this year. The total was still higher than May’s $25.66 billion.
This suggests the drop reflects a return to normal trading patterns after a major sports event. It does not necessarily point to a longer term slowdown.
Legal Pressure and Sports Expansion Continue
Both platforms are dealing with more scrutiny from state regulators in the US. Much of the focus is on sports related contracts.
Over a dozen states have taken enforcement action or filed lawsuits against Kalshi and Polymarket. Connecticut is the latest to escalate its fight.
Last week, Connecticut sued Kalshi to try to block the platform from offering sports contracts. The lawsuit adds to a legal battle between the state and the company that has been building for months.
Despite the legal pressure, Kalshi has kept expanding its sports business. The company recently signed a deal with the US Tennis Association.
That deal makes Kalshi the exclusive prediction market partner of the US Open. The tournament’s main draw began August 30.
Kalshi also took action against a high profile user this week. The company permanently banned former US Representative George Santos from trading on its platform.
It was Kalshi’s first ever permanent ban. Santos broke platform rules by trading a bet on whether he would attend the State of the Union.
He was ordered to pay a fine of more than $71,000 as part of the earlier settlement tied to that trade. The permanent ban followed shortly after.
Together, the numbers show a market that grew fast during the World Cup and has since cooled. Kalshi remains the larger of the two platforms by volume.
Both companies continue to expand their sports offerings even as state regulators push back. The coming months will show whether volume keeps settling or picks back up again.
