The rivalry between Polymarket and Kalshi is intensifying with the former compiling a copycat dossier that documents instances it alleges Kalshi has stolen ideas. At the same time, Polymarket has followed Kalshi’s lead by filing a lawsuit against the state of Minnesota.
The two companies’ fates appear to be interlinked as state regulators target prediction market platforms, accusing them of running an illegal gambling operation.
Despite their similarities, there is no love lost between the two New York-based businesses. Polymarket is now accusing Kalshi of spying on its offices in New York.
“There have been a couple too many coincidences,” Polymarket’s head of marketing, Matthew Modabber, told The New York Post. “There is bad intention in how they copy us. They’re breathing down our neck.”
Is Kalshi Spying?
Polymarket’s office is located across the street from a building leased by Paradigm, a venture capital firm that has invested in Kalshi. Polymarket employees allege that Kalshi could be using the space to spy through the windows.
“We got together and discussed, like, ‘Is this possible?’” said one employee. The group concluded that, “With Kalshi, it is,” the source said.
Kalshi and Paradigm both dismissed the accusations. “This is laughable,” said a Paradigm spokesperson.
“This is sad and borderline delusional,” said Kalshi spokesperson Jack Such. “Polymarket is welcome to waste its time investigating. While they do that, we’ll keep building.”
What’s in the Dossier?
The discussions about Kalshi potentially spying on Polymarket followed Kalshi’s launch of a free grocery campaign, just as Polymarket was planning to open its grocery pop-up store. Kalshi announced its promotion on February 2.
Polymarket announced its pop-up store the next day, which it said had taken months of planning.
“They seemed to know we were going to announce that day,” said a Polymarket insider, referencing Kalshi. “To us, the timing was pretty suspicious.”
Suspicious Timing of Similar Announcements
On June 10 last year, Webull announced that it would launch Kalshi’s hourly crypto markets. The same day, Polymarket also announced that it had launched hourly crypto markets.
Polymarket again alleges that the timing of Kalshi and Webull’s announcements, which were on the same day as it launched its new product, is suspicious.
“Kalshi has offered these products since well before June 10, 2025,” said Such. “That was just the day that Webull started to offer them. The fact that Polymarket announced this product long after we had actually launched should make it obvious who is copying whom.”
Polymarket’s founder and CEO, Shayne Coplan, has called Kalshi a “copycat” site. Kalshi CEO Tarek Mansour responded in kind, saying that the acquisition of QCEX by Polymarket was “super normal for competition to basically want to follow.”
Ads Also Mimic Each Other
Both companies have run ad campaigns targeting users in states where sports betting is illegal. Polymarket alleges that Kalshi copied its ad campaign in California. On Friday, August 22, 2025, Polymarket began advertising in California for soccer matches with the “Hey California” tagline.
On Monday, August 25, Kalshi launched an ad campaign in California, which also featured the tagline “Hey California.”
“Attributing this coincidence to corporate espionage is delusional,” said Such. He insisted that Polymarket has no trademark over the phrase “Hey California,” which is “extremely common.”
Polymarket Copies Kalshi in Suing Minnesota
The campaigns to attract users in states that have not yet legalized sports betting have led to legal battles across the country.
Polymarket, this week, followed Kalshi in filing a lawsuit against Minnesota after the state approved a ban on a wide range of prediction markets.
“When it goes into effect in less than two months, Polymarket US will face a credible threat of imminent
criminal prosecution—forcing it either to cease lawful and constitutionally protected conduct or risk felony criminal liability,” states the lawsuit.
The CFTC has also filed a lawsuit against Minnesota, claiming it has exclusive jurisdiction over prediction markets. Both Kalshi and Polymarket are licensed by the regulator.
While their fates are intertwined, there is no sign that Kalshi and Polymarket are willing to assist each other.
