Mamdani campaigned on an ambitious agenda, including universal child care, a free bus system and freezing rent prices for certain rental units in the city.

New York Attorney General Letitia James, left, administers the oath of office to mayor-elect Zohran Mamdani, center, as his wife, Rama Duwaji, holds two Qurans on Thursday in New York.Yuki Iwamura / AP

New York Mayor Zohran Mamdani officially became the 111th mayor of the nation`s largest city early Thursday as he seeks to carry out the transformative progressive platform on which he campaigned.

New York Attorney General Letitia James swore in Mamdani, the city`s first Muslim mayor, in a small ceremony with his family just after midnight. Supporters counted down the seconds.

"This is truly the honor and the privilege of a lifetime," Mamdani said at the swearing-in ceremony at the old City Hall IRT subway station, which was closed in 1945.

Mamdani ran on a platform advocating public transit. He called the ornate station "a testament to the importance of public transit to the vitality, the health, and the legacy of our city."

Mamdani took the oath with his hands on two Qurans - one belonging to his grandfather and the other from the New York Public Library`s Schomburg Center for Research in Black Culture. The library`s book is believed to have been made in Ottoman Syria in the 1800s, the library system said.

Later Thursday, Mamdani plans to host a larger inauguration ceremony and block party, where Sen. Bernie Sanders, I-Vt., will administer a ceremonial, public oath of office to the new mayor. Mamdani said 4,000 people were invited to the ceremony but that the block party was open to "everyone."

"We wanted to ensure that as we celebrated the beginning of our administration, it was a celebration that was not simply for the typical people who would be invited to an inauguration, but in fact, for everyone," Mamdani told reporters last week during a press conference, previewing the events.

"This is not my success, it`s our success. It`s not my administration, it`s our administration. Similarly, it`s not my inauguration. It`s for all of us," Mamdani added.

Mamdani said he felt confident that he`ll have the staff and appointed officials in place on time to begin the work of his administration.

"We will have the people in place necessary to start to deliver, not only on our affordability agenda, but frankly, to deliver on the day-to-day services that New Yorkers require," Mamdani told reporters.

The next key date early in Mamdani`s administration will be Jan. 7 - the first day of New York`s 2026 state legislative session in Albany.

Mamdani last year campaigned on an ambitious agenda aimed at lowering costs for New Yorkers, including by promising to make childcare universal and free, implement a free bus system and freeze rent prices for certain rental units in the city.

Sen. Bernie Sanders, I-Vt., and Rep. Alexandria Ocasio-Cortez, D-N.Y., at a rally with Zohran Mamdani on Oct. 26.Heather Khalifa / AP file

Mamdani has said that the bulk of the money to pay for his agenda would come from raising taxes on New Yorkers who make over $1 million. But in order to raise taxes in the city, the new mayor will need approval from state leaders.

While Democratic leaders in the Legislature have previously been open to raising taxes on high-income individuals and corporations, Gov. Kathy Hochul, D-N.Y., has always been staunchly opposed to raising taxes on anyone in New York.

Hochul, who is running for re-election this year, in a recent interview she left the door open to finding other revenue streams - such as raising corporate taxes - to fund Democratic priorities throughout the state.

"It is my job as governor to make sure that whomever the mayor is, they`re successful," Hochul told WNYW-TV in December.

"The budget process is unfolding. We`ll be working with the legislators over the next couple months, and we`ll find out how we can take off a bite of what we need to do - like what is doable in this upcoming year, in the following year," she added.