NFL betting has grown for years, climbing to approximately $30 billion, but the boom is showing signs of stalling at U.S. sportsbooks as prediction markets gain ground.

The American Gaming Association estimates that $29.5 billion will be bet on the 2026 NFL season with domestic sportsbooks, up just 0.3% from last season’s figure based on revenue reports from state gaming regulators.

Missouri is the only state to launch legal betting since 2025, contributing to the stalled growth of the sportsbook industry, but the rise of prediction markets is believed to be a major factor, according to the AGA.

From last September through May, the amount bet with U.S. sportsbooks grew by 4%, after having grown by 14% over the same period the previous year, according to the AGA. Last football season was the first that prediction markets such as Kalshi began offering a large menu of sports markets.

Experts expect NFL trading volume on prediction markets to double this season, potentially reaching $36.8 billion, according to analysis from Rotowire.com. Prediction market volume differs somewhat from betting handle because the contracts can change hands multiple times.

Industry research firm Eilers & Krejcik Gaming found that NFL trading volume on prediction markets in August was 4.6 times higher than last August.

Prediction markets have taken off despite legal challenges and concerns from the NFL. Last week, a federal appeals court ruled that Nevada could enforce its gaming regulations to prohibit Kalshi from offering trading on sports in the state. On Wednesday, New Jersey asked the U.S. Supreme Court to weigh in on the legality of prediction markets.

The NFL sent a letter to prediction market operators this week, expressing concern that some markets being offered threaten the integrity of the sport.

“It is deeply concerning that bets within the objectionable categories that we identified months ago have been and continue to be listed as contracts on exchanges,” Sabrina Perel, the NFL’s chief compliance officer, wrote in the letter obtained by ESPN.

AGA CEO and president Bill Miller, in a release announcing the lobbying group’s annual NFL betting estimate, accused prediction markets of “misleading” consumers, refusing to follow state and tribal sports betting laws, and avoiding gaming taxes.

“Their defiance means consumers, including teenagers and freshmen, placing bets without the protections, oversight and accountability that the legal market provides,” Miller said.

Prediction markets allow customers 18 or older to trade, while the legal age for regulated sportsbooks is 21 in most states. The Coalition for Prediction Markets did not respond to a request for comment from ESPN.

The NFL season kicks off Wednesday with a Super Bowl rematch between the Seattle Seahawks and New England Patriots.