Ken Griffin, Mayor Mamdani clash over NYC tax proposal

NEW YORK - A war of words is escalating between hedge fund billionaire Ken Griffin and Mayor Mamdani, underscoring growing tensions over taxing the ultra-wealthy and the future of business in New York City.

What we know:

The dispute was sparked after Mamdani posted a video outside Griffin’s $238 million Midtown penthouse, voicing support for a proposed "pied-à-terre" tax on high-value second homes. The mayor used Griffin’s property as a real-world example of the kind of wealth the tax would target.

Mamdani and billionaire Ken Griffin clash over a proposal targeting luxury second homes

Griffin, the CEO of Citadel, sharply criticized the move, calling the video "creepy," "weird" and "frightening." He argued the mayor jeopardized his safety by publicly identifying his residence at a time of heightened political violence.

Mamdani, however, is standing firm.

Who is Ken Griffin?

Ken Griffin is a major hedge fund and financial services firm he launched in 1990. 

He is one of the wealthiest people in the world and a prominent figure in U.S. finance, with significant investments in markets, real estate and philanthropy. 

Griffin has also been an influential political donor and has expanded Citadel’s footprint beyond New York, including major operations in Miami.

What is Giffin's net worth? 

According to Frobes, Griffin's net worth is just over $50.2 billion.

He's reportedly given some $2.4 billion to philanthropic causes. Recent beneficiaries include Memorial Sloan Kettering Cancer Center and nonprofit hospitals in Miami.

Mamdani's tax video outside $238M penthouse

What they're saying:

"I want all New Yorkers to succeed. And that also includes Ken Griffin, who is a major employer in our city," the mayor said. "That does not negate the fact, however, that our tax system is fundamentally broken. It rewards extreme wealth while working people are pushed to the brink."

The mayor said he has not spoken with Griffin since posting the video, but doubled down on his push for what he calls "meaningful tax reform."

Gov. Hochul's pied-à-terre proposal explained

At the center of the debate is the proposed pied-à-terre tax, backed by New York Kathy Hochul, which would apply to second homes valued at more than $5 million. The measure is still being negotiated as part of the state budget, which is already more than a month overdue.

Griffin’s company, Citadel, said it has paid nearly $2.3 billion in city and state taxes over the past five years. Still, the billionaire warned the mayor’s actions could have broader economic consequences.

Speaking at a conference this week, Griffin said the controversy is pushing him to deepen investments in Florida instead of New York.

What is Griffin saying?

"What the mayor of New York has made clear to my partners … is that we need to double down on our bet in Miami," Griffin said, citing a desire to operate in a state that "embraces business" and "personal freedom."

He also raised questions about the future of a planned Park Avenue project that he said could generate 15,000 permanent jobs.

The clash comes as some business leaders voice concern about the city’s economic direction. Critics note Mamdani has yet to appoint a head of the Economic Development Corporation, one of the city’s key agencies for job growth, more than five months into his term.

What's next:

For now, the fight between one of the world’s most powerful hedge fund managers and New York City’s mayor is shaping up as a broader test of how far the city is willing to go in taxing wealth, and how businesses may respond.

What is a pied-à-terre tax?

The tax would apply to second homes in the city valued at more than $5 million and is aimed at generating revenue from high-value properties often left unoccupied.

Griffin, whose net worth is estimated at about $50 billion, criticized the mayor’s approach.

Zohran MamdaniEconomy