Kalshi, Polymarket take early lead over prediction market rivals for first week of the NFL season

Before Patrick Mahomes laced up his cleats for his 2026-2027 NFL regular-season debut, US prediction markets already cleared a historic benchmark for the opening week of the season.

Two operators alone — Kalshi and Polymarket — topped the combined $1 billion mark in NFL trading activity over the first six days of Week 1, according to numerous measures this week. During the period, Kalshi recorded NFL volume of $983.4 million, according to DeFi Rate, earning the pole position by a large margin. Mahomes and the Kansas City Chiefs thrashed the Denver Broncos 31-10 on Monday Night Football, capping the largest week for prediction markets ever.

Even before the primetime matchup in Kansas City, it became abundantly clear that the industry would shatter previous marks for weekly activity. The AFC West showdown bolstered the already robust totals. Overall, volume for the week hit a record $15.9 billion, according to Bank of America, up 16% from a week earlier.

The pure-play prediction market-operators, Polymarket and Kalshi, emerged from Week 1 as the clear winners. On one hand, Kalshi’s market share led narrowed over its competitors, falling to 82% for the week ended 13 September, down from 86% a week earlier.

Still, Kalshi had a nine-fold lead over Polymarket, its next closest rival. Polymarket, meanwhile, led the group with 762,000 app downloads, edging Kalshi, DraftKings and FanDuel in the category. The downloads represented a 13,509% weekly increase and 25% of total category downloads, Polymarket wrote in a statement.

Uptick at Robinhood

Across the market, operators delivered high double-digit gains compared with Labor Day weekend, which featured a full slate of college football games but no NFL contests. Two operators, DraftKings and Underdog each saw triple-digit growth, delivering weekly increases of 125% and 119%, respectively. Three others, Polymarket, Crypto.com and Novig, saw gains of at least 30%, led by Polymarket with a weekly increase of 46%.

One interesting nugget surrounds weekend figures at Kalshi, where volume on Sunday only surpassed prior daily activity by $34 million, BofA data shows. Typically, Sunday volume for the quarter dwarfs that of College Football Saturdays due to the voracious demand for NFL offerings. BofA analyst Shaun Kelley attributes the irregularity to the possibility that Kalshi is “over indexing” on college sports.

Kelley also cited improvements at Robinhood as a possible factor for the regression at Kalshi. Just before the NFL season, Robinhood took a minority stake in Crypto.com and struck a deal to begin routing NFL contracts to OG.com, the site’s regulated prediction market platform.

A 40% weekly increase at Crypto.com combined with the attrition at Kalshi may reflect the enormity of the Robinhood deal, according to Kelley.

Glitzy primetime matchups

With all activity, beyond just football, Crypto.com recorded trading volume of $350 million for the week, figures from The PM Pulse show. The newsletter, which is in partnership with Aldrin Research for monitoring industry trends, indicated that Crypto saw weekly growth of 41%. While Kalshi and Polymarket accounted for more than $15 billion in weekly volume, four others recorded activity of at least $300 million. Buoyed by a popular Sydney Sweeney ad, Novig increased volume by nearly 34% on the week.

Moving forward, prediction markets could see a bump from appearances by several high-profile teams in primetime during Week 2. On Thursday, the Buffalo Bills will make their regular-season debut at Highmark Stadium against the Detroit Lions. Enthusiasm among supporters of the “Bills Mafia” for the opening of the $2.2 billion stadium could pad weekly totals on prediction markets. New York is one of the nation’s largest markets for sports betting and predictions.

The week will conclude with a matchup on Monday Night Football between the New York Giants and the Los Angeles Rams, the putative Super Bowl favourite. On Kalshi, the Rams had a 75% probability to defeat the Giants as of Wednesday afternoon.

“It’s going to be a great test for our team,” said Giants quarterback Jaxson Dart on Wednesday.