As the NFL regular season kicked off with Patrick Mahomes taking the field for his 2026-2027 debut, US prediction markets were already making headlines with record-breaking trading activity for the first week. In the first six days of Week 1, Kalshi and Polymarket reached a historic combined total of over $1 billion in NFL trading. Kalshi led the pack with an impressive $983.4 million in trading volume, according to data from DeFi Rate. The Kansas City Chiefs, led by Mahomes, sealed a dominant 31-10 victory over the Denver Broncos on Monday Night Football, marking the culmination of a week of unparalleled activity for prediction markets.
Before the Chiefs' game, it was evident that the industry was on track to exceed its previous weekly activity records. The AFC West matchup only bolstered these impressive totals, culminating in a weekly volume that hit a staggering $15.9 billion, a 16% increase from the previous week, as reported by Bank of America.
In this competitive landscape, Kalshi and Polymarket emerged distinctly as the top players following Week 1. Notably, Kalshi reached a market share of 82% for the week ending September 13, down from 86% the week prior, yet still held a considerable nine-fold lead over Polymarket, its nearest competitor. Polymarket, however, took the lead in another arena, with 762,000 app downloads that week, surpassing Kalshi, DraftKings, and FanDuel. This marked a significant 13,509% weekly increase, comprising 25% of all downloads in the category, as stated by Polymarket.
Comparisons to Labor Day weekend reveal significant growth across the board. DraftKings and Underdog posted impressive triple-digit increases of 125% and 119%, respectively, while Polymarket experienced a notable weekly growth of 46%. In contrast, Kalshi saw a modest $34 million increase on Sunday compared to previous days, as noted in Bank of America data. Typically, NFL activity on Sundays would far exceed that of college football Saturdays, leading BofA analyst Shaun Kelley to suggest that Kalshi might be "over indexing" on college sports.
Kelley also pointed to the recent developments at Robinhood, which may have impacted Kalshi's numbers. Robinhood took a minority stake in Crypto.com and negotiated to start routing NFL contracts to OG.com, the regulated prediction market platform associated with Crypto.com. This partnership likely contributed to a 40% increase in trading volume at Crypto.com and highlighted a potential shift in market dynamics away from Kalshi.
In total, Crypto.com tallied $350 million in trading volume for the week, reflecting a 41% growth according to The PM Pulse, a newsletter by Aldrin Research monitoring market trends. While Kalshi and Polymarket accounted for over $15 billion in volume, four other operators recorded at least $300 million, boosted by a well-received advertisement featuring Sydney Sweeney, which helped Novig increase its volume by nearly 34%.
Looking ahead, prediction markets anticipate heightened activity during Week 2 with several high-profile NFL matchups in primetime. The Buffalo Bills will debut at their new $2.2 billion Highmark Stadium against the Detroit Lions, likely energizing the "Bills Mafia" and potentially increasing trading volumes. The week will conclude with a Monday Night Football game featuring the New York Giants versus the Los Angeles Rams, the presumed favorites for the Super Bowl. As of Wednesday afternoon, the Rams had a 75% probability of beating the Giants, according to Kalshi.
Giants quarterback Jaxson Dart spoke on Wednesday, stating, "It’s going to be a great test for our team."
