Zohran Mamdani was sworn in as New York City’s mayor on Thursday, beginning his four-year term with a midnight oath followed by a larger public inauguration later in the day.

City law requires mayoral terms to begin on Jan. 1 following an election, and New York has long observed the tradition of a low-key midnight swearing-in to ensure a clear transfer of authority. Mamdani took his oath at the closed Old City Hall subway station, a rarely accessed historic site beneath Manhattan.

Mamdani’s transition team said the location was chosen to reflect his focus on working-class New Yorkers.

The 34-year-old former state lawmaker campaigned on affordability, pledging to freeze rents, expand free bus service and broaden access to childcare. His platform helped drive record turnout, with more than 2 million voters casting ballots. Mamdani won about 50% of the vote, finishing well ahead of former Governor Andrew Cuomo, who ran as an independent, and Republican candidate Curtis Sliwa.

New York Attorney General Letitia James administered the midnight oath. James was among Mamdani’s early supporters and has played a visible role in state politics in recent years.

Political observers said her participation signaled Mamdani’s alignment with progressive Democratic leaders. Grant Reeher, a political science professor at Syracuse University, said the choice underscored Mamdani’s intention to govern independently of the White House.

Born in Uganda, Mamdani becomes New York City’s first Muslim mayor. He has been outspoken on issues such as immigration and affordability and has described his policy differences with President Donald Trump as significant.

Mamdani has frequently cited former Mayor Bill de Blasio as a political influence. De Blasio also began his first term with a private swearing-in by the state attorney general, followed by a public ceremony later that day.

Senator Bernie Sanders, whom Mamdani has called a major inspiration, is scheduled to take part in the public inauguration ceremony, along with U.S. Representative Alexandria Ocasio-Cortez.

The public event includes a ceremony on the steps of City Hall and a program of speeches and music for thousands of invited guests in City Hall Plaza. The city has also arranged free viewing areas and a livestream along Broadway.

Campaign finance disclosures show Mamdani raised about $2.6 million for inauguration and transition events from nearly 30,000 contributors, the highest total for a New York mayoral inauguration this century.

After taking office, Mamdani is expected to move from his rent-stabilized apartment in Astoria to Gracie Mansion, the mayor’s official residence on Manhattan’s Upper East Side.

While some business leaders initially expressed concern about Mamdani’s democratic socialist platform, city officials and financial institutions have since begun exploring how to work with the new administration.