Polymarket’s monthly trading volume fell to $8.41 billion in August, down about 35% from July’s $12.89 billion, as the post-World Cup slowdown cooled prediction-market activity after a record summer run. Data compiled by The Block shows the decline was concentrated on Polymarket’s core international platform, which slid from $7.89 billion in July to $4.59 billion in August, while Polymarket US eased from $5.00 billion to $3.82 billion.
By contrast, rival Kalshi barely flinched. Kalshi closed June at $33.00 billion, climbed to $40.10 billion in July, and only retreated to $38.67 billion in August, a drop of roughly 4%. That means Kalshi processed nearly five times Polymarket’s monthly volume in August. DeFiLlama data indicates the broader pullback extended into early September, with weekly industry volume around $4.00 billion, well below the July 22 peak of $5.60 billion that was driven by World Cup betting interest.
Despite the volume slowdown, investor appetite remains strong. Donald Trump Jr.’s venture capital firm, 1789 Capital, is leading a $1 billion funding round that values Polymarket at $21 billion, a 40% increase from its earlier valuation of about $15 billion. Predictefy metrics put Polymarket’s rolling 30-day volume at $3.80 billion versus $11.28 billion for Kalshi, although Polymarket still counts more than 3 million users.
Legal pressure also continues to build. Baltimore has sued both Kalshi and Polymarket, alleging they are running unlicensed sports betting operations. Kalshi is separately fighting a lawsuit from New York Attorney General Letitia James, a dispute that prompted the CFTC to invoke emergency powers to keep the platform running in the state. Both platforms face additional court hearings scheduled for the fourth quarter of 2026.
