Adams, 64, entered the plea before US Magistrate Judge Katharine Parker at his first appearance in the case in Manhattan federal court.
"I am not guilty, your honour," Adams said when Parker asked for his plea.
Adams had previously denied wrongdoing and said he would fight the charges in court.
His lawyer, Alex Spiro, said he would file a motion to dismiss the charges next week.
Members of the US Marshals Service escorted Adams and Spiro out of the courtroom.
Parker said she would release Adams on his own recognisance on the condition that he not have contact with witnesses or people named in the indictment.
She said there would be exceptions for staff and family members, so long as he does not discuss the details of the indictment with them.
"I will continue to do my job as mayor," Adams said at a news conference on Thursday.
In an indictment returned by a grand jury on Tuesday and unsealed on Thursday, federal prosecutors said Turkish diplomats and businesspeople illegally funnelled money to Adams' campaign and showered him with luxury travel perks, including rooms at opulent hotels and meals at high-end restaurants.
In exchange, Adams in 2021 pressured city officials to allow Turkey's new 36-storey consulate to open despite safety concerns, according to prosecutors.
The alleged scheme dates back to 2014 when Adams became Brooklyn borough president, prosecutors said.
The illegal campaign contributions helped finance his 2021 campaign for mayor, prosecutors said.
The Democrat faces five criminal charges and could face decades in prison if found guilty.
Turkey's foreign ministry, president's office and Washington DC embassy did not respond to requests for comment.
Adams, a former police officer who rose to the rank of captain, is the first of the city's 110 mayors to be charged with a federal crime while in office.
The United States' largest city has been in a state of political upheaval for the past month as federal probes swirled around senior officials.
The police commissioner resigned on September 12 after FBI agents seized his phone.
Days later, Adams' top legal adviser stepped down.
Several prominent city officials and lawmakers, including US Representative Alexandria Ocasio-Cortez, have called on Adams to resign.
But two powerful Democratic lawmakers from Brooklyn, Senate Majority Leader Chuck Schumer and House Minority Leader Hakeem Jeffries, stopped short of doing so.
According to the indictment, Adams accepted free travel from a Turkish airline worth tens of thousands of dollars while serving as Brooklyn borough president and paid $US600 ($A870) to stay two nights at a luxury suite in the St Regis hotel in Istanbul, well below the actual cost of $US7000.
Prosecutors said Adams would fly on the Turkish airline even when it was inconvenient.
"You know first stop is always Istanbul," he wrote in a 2017 text message when his partner expressed surprise that they were flying from New York to Paris through Istanbul.
For his 2021 mayoral campaign, Adams disguised campaign contributions from Turkish sources by funnelling them through US citizens, the indictment said.
Those funds allowed Adams to qualify for an additional $US10 million in public financing, according to the indictment.
US law forbids foreign contributions to local political campaigns.
Prosecutors say Adams responded to Turkish concerns.
Acting on a request by a Turkish diplomat, Adams pressured city safety inspectors to allow the country's new consulate to open in time for a September 2021 visit by Turkish President Tayyip Erdogan, even though it would have failed a fire inspection, the indictment said.
After repeated messages about the building from Adams, a senior Fire Department official allegedly told a subordinate he would lose his job if he did not allow the consulate to open, according to prosecutors.
Adams notified the diplomat when the Fire Department approved the building to open later in the day, the indictment said.
"You are a true friend of Turkey," the diplomat allegedly responded
