As Patrick Mahomes prepared for his 2026-2027 NFL regular-season debut, the U.S. prediction markets marked a historic achievement, achieving over $1 billion in NFL trading activity during the opening week. Kalshi and Polymarket were the standout operators, with Kalshi generating a record $983.4 million in NFL volume, outpacing all its competitors. This record-setting week culminated in the Kansas City Chiefs' decisive 31-10 victory over the Denver Broncos on Monday Night Football, making it the busiest week for prediction markets to date.
Before the high-profile game in Kansas City, the momentum was already evident as the industry was on track to exceed prior weekly records. Following the AFC West clash, the overall volume for the week reached an unprecedented $15.9 billion, reflecting a 16% increase from the previous week, according to Bank of America.
In the prediction market sphere, Polymarket and Kalshi emerged as leading figures. Despite Kalshi's market share dipping to 82% for the week ending September 13, down from 86% the previous week, it maintained a significant nine-fold advantage over Polymarket, its closest competitor. Polymarket also led in app downloads, surpassing all others with 762,000 downloads, achieving a massive 13,509% increase from the previous week and accounting for 25% of all downloads in this sector.
The overall market exhibited strong growth compared to Labor Day weekend, which saw no NFL games. DraftKings and Underdog reported impressive triple-digit growth rates, with increases of 125% and 119%, respectively. Other operators also saw gains, including Polymarket, Crypto.com, and Novig, each logging at least 30% growth, with Polymarket leading at 46%.
Interestingly, Kalshi's Sunday trading volume increased by only $34 million compared to previous days, a notable anomaly given the typical surge in NFL demand over college football weekends. Analyst Shaun Kelley from Bank of America suggested that Kalshi may be disproportionately focusing on college sports. Furthermore, he indicated that improvements at Robinhood, which had recently taken a minority stake in Crypto.com, may have impacted Kalshi's performance. Robinhood's new agreement to route NFL contracts to OG.com could have contributed to the changes seen in Kalshi's metrics.
Crypto.com reported a trading volume of $350 million for the week, alongside a 41% growth rate, while Kalshi and Polymarket combined for over $15 billion in activity. Four other platforms also reported volume exceeding $300 million, with Novig benefiting from a high-profile advertisement featuring Sydney Sweeney, which helped boost their weekly volume by nearly 34%.
Looking ahead, prediction markets could see increased activity thanks to several high-profile teams appearing in primetime during Week 2. The Buffalo Bills are set to debut at their $2.2 billion Highmark Stadium against the Detroit Lions, likely generating excitement among "Bills Mafia" supporters. The week will conclude with a Monday Night Football matchup between the New York Giants and the Los Angeles Rams, who were given a 75% probability of victory over the Giants on Kalshi as of Wednesday afternoon. Giants quarterback Jaxson Dart remarked on the challenge, stating, "It’s going to be a great test for our team."
