<p>Combined monthly volume across Kalshi, Polymarket, and Polymarket US fell 14.5% in August 2026 to $45.33 billion, the first month-over-month decline since August 2025.</p><p>The drop followed a summer peak driven by the FIFA World Cup, which ran from June 11 to July 19 and drew heavy activity to both platforms. Despite the decline, August volume came in well above May's $25.66 billion, before the tournament began.</p><p>Kalshi recorded $37.17 billion in August, down 7.3% from $40.1 billion in July. Polymarket and its US platform together posted $8.16 billion, a 36.7% drop from their combined $12.89 billion the prior month.</p><h2 id="a-post-world-cup-correction">A Post-World Cup Correction</h2><p>Both platforms are also contending with mounting legal pressure from state regulators. More than a dozen states have taken enforcement action or filed lawsuits against Kalshi and Polymarket, with most disputes centered on sports-related contracts.</p><p>Connecticut recently sued Kalshi on Aug. 27, seeking to block it from offering sports contracts. The lawsuit followed months of legal conflict between the state and the company over the same issue.</p><p><strong>Related Article: <a href="https://coinmarketcap.com/academy/article/kalshi-perpetual-futures-us-stock-index-copper-cftc" rel="noopener noreferrer">Kalshi Files for Perpetual Futures on US Stock Index and Copper</a></strong></p><h2 id="kalshi-signs-us-open-deal-and-issues-first-permanent-ban">Kalshi Signs US Open Deal and Issues First Permanent Ban</h2><p>Kalshi has moved to expand its sports presence despite the legal environment. It reached an agreement with the US Tennis Association to serve as the exclusive prediction market partner of the US Open, whose main draw began Aug. 30.</p><p>On Aug. 31, Kalshi issued its first-ever permanent ban, removing former US Representative George Santos from the platform. Santos had placed a bet on whether he would attend the State of the Union, which violated platform rules. He was ordered to pay a fine exceeding $71,000.</p>

Kalshi and Polymarket August Volume Drops 15% in First Monthly Decline Since 2025

Table of Contents

Other articles published on Sep 2, 2026

Thailand Adopts Crypto Travel Rule With Self-Custodial Wallet Checks

Japan's Remixpoint Sells All Altcoins, Goes Bitcoin-Only With 1,506 BTC

Adam Back Invests $8.8M in Capital B as Firm Targets 3,521 BTC

Join our free newsletter for daily crypto updates!