Prediction Markets Hit $14.1B in NFL Kickoff Week — Kalshi Holds 92% Market Share
Combined weekly contract volume across Kalshi and Polymarket reached $14.1 billion in the week of September 7-13, the first full NFL regular season week, driven by football, the US Open, Fed rate decision bets, and esports. Kalshi recorded $12.98 billion — 92.1% of total — while Polymarket Global recorded $1.11 billion. NFL-specific volume on Kalshi alone hit $983 million for the week, up 1,288% week-over-week. Non-sports categories reached $10 billion, a sixth consecutive weekly record. Analysts project NFL season prediction market volume could reach $57 billion across all platforms.
Combined weekly contract volume across Kalshi and Polymarket Global reached $14.1 billion in the week of September 7-13, 2026 — a 9.3% increase from the prior week's $12.9 billion — as the NFL regular season opened alongside the US Open tennis final, a Federal Reserve rate decision on September 15-16, and major esports events. Kalshi recorded $12.98 billion for the week, capturing 92.1% of the combined Kalshi-Polymarket volume. Polymarket Global recorded $1.11 billion, a 7.6% weekly increase. NFL-specific contract volume on Kalshi reached $983 million for the week, up 1,288% from the preseason weeks. On the first Sunday of the NFL regular season alone, Kalshi saw $388 million in NFL game contracts — 76% of all NFL prediction market volume recorded that day across platforms. Full-season analysts at DeFi Rate project total NFL prediction market volume could reach $57 billion across all platforms by the end of the 2026-27 season.
The 92% Kalshi share of combined Kalshi-Polymarket volume represents a dramatic shift from just three months ago, when the split was close to even. The divergence has three primary causes. First, Kalshi launched perpetual futures (crypto in May, gold/silver in September) that drive large-notional non-sports volume — Polymarket's global perps product, launched September 3, is not yet generating comparable US-accessible volume. Second, Kalshi's institutional broker network through Cantor Fitzgerald and Susquehanna brings large-ticket block trades that inflate notional figures. Third, Polymarket US (the CFTC-regulated entity) is operating under tighter contract constraints than Kalshi, which has a broader self-certified contract menu. Non-sports weekly volume across platforms hit $10 billion in the same week, the sixth consecutive record — Kalshi accounted for $9.6 billion of that, Polymarket Global for $344 million.
The NFL volume numbers require context. The $983 million in Kalshi's NFL-specific volume for Week 1 does not include DraftKings Predictions, Robinhood Derivatives, Coinbase, or other CFTC-registered platforms. Total NFL prediction market volume across all platforms for Week 1 exceeded $3 billion, according to Covers data — meaning Kalshi held approximately 33% of NFL prediction market volume across all platforms, with DraftKings, Robinhood, and others accounting for the remaining two-thirds. Within the Kalshi-Polymarket duopoly that most volume reporting tracks, Kalshi's NFL dominance is higher, but the full platform ecosystem distributes volume more broadly. The $57 billion full-season NFL projection for all prediction market platforms implies weekly volumes above $3 billion sustaining through the regular season, playoffs, and Super Bowl — a trajectory that, if achieved, would make NFL prediction markets comparable in scale to the total US sportsbook handle in a comparable period.
The volume figures arrive in the same week that the sector faces its densest legal calendar since the litigation began. Washington's September 2 multi-source geofencing deadline passed two days before NFL Week 1 opened. Michigan's Robinhood deal runs through October 9. The Ninth Circuit en banc petition (Kalshi) and Robinhood's SCOTUS petition are both pending. The Massachusetts SJC decision could arrive any day. New Jersey's SCOTUS cert petition is docketed and awaiting Kalshi's response. The $14.1 billion weekly volume number puts a dollar figure on what is at stake in those proceedings: the commercial value of operating prediction markets at scale during NFL season is measured in the tens of billions annually, and the legal question of whether states can restrict that access is being litigated while the market runs at record pace.
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Recent updates
Missouri AG Sends Cease-and-Desist Letters to Six Prediction Market Operators
Missouri Attorney General Catherine Hanaway issued cease-and-desist letters on September 18 to six prediction market operators — Kalshi, Polymarket, Robinhood, Crypto.com, Novig, and Underdog — alleging their sports event contracts constitute unlicensed sports wagering under Missouri law. The letters give platforms 30 days to comply or obtain licenses from the Missouri Gaming Commission. Missouri is the broadest multi-platform C&D action to date, targeting all major operators simultaneously. The action arrives one day after Montana and Kalshi filed a joint stipulation in which Montana agreed to pause enforcement while Ninth Circuit en banc review is pending.
Yahoo Finance Ends Polymarket Data Partnership After Five Months
Yahoo Finance and Polymarket mutually ended their prediction market data partnership on September 18, approximately five months after the companies announced an exclusive arrangement in November 2025. The Polymarket data hub that Yahoo Finance launched in January-February 2026 was quietly taken down in April 2026. No reason was publicly disclosed. Yahoo Finance retains an advertising relationship with Polymarket. The partnership's end is a setback for Polymarket's strategy of embedding its probability data into mainstream financial media platforms.
Montana and Kalshi Reach Joint Stipulation — State Pauses Enforcement Pending Ninth Circuit En Banc
Kalshi dismissed its lawsuit against the Montana Department of Justice on September 17 after both sides filed a joint stipulation in which Montana agreed to pause all enforcement, investigations, and cease-and-desist proceedings against Kalshi's event contracts. The pause lasts until the Ninth Circuit either denies en banc review of the August 28 ruling or issues an en banc decision. Montana must give Kalshi 30 days written notice before resuming any enforcement action after that window closes. The agreement mirrors the Robinhood-Michigan stipulation from September 4 and reinforces a pattern of states reaching negotiated compliance pauses while the appellate process plays out.