Trump, a Republican, has been fighting James in court over her investigation, which he has called a politically motivated witch hunt. During oral arguments Monday, Trump attorney Alina Habba said that "Donald Trump does not believe he is above the law".
Habba said that the ruling will be appealed.
"We respectfully disagree with the court's decision. All documents responsive to the subpoena were produced to the attorney general months ago," she said.
James has been conducting a lengthy investigation into the Trump Organisation, the former president's family company, centring around what she has claimed is a pattern of misleading banks and tax authorities about the value of his properties.
"Today, justice prevailed," James said after Engoron's ruling. "For years, Donald Trump has tried to evade the law and stop our lawful investigation into him and his company's financial dealings. Today's ruling makes clear: no one is above the law."
The contempt finding by the judge came despite a spirited argument by Habba, who insisted repeatedly that she went to great lengths to comply with the subpoena, even travelling to Florida to ask Trump specifically whether he had in his possession any documents that would be responsive to the demand.
The judge, though, criticised the lack of explanation in the Trump team's formal response to the subpoena, telling Habba: "You can't just stand here and say I searched this and that".
And after saying he felt "like there's an 800-pound gorilla in the room here," he asked why the response to the subpoena didn't include an affidavit from Trump.
Habba noted that Trump does not send emails or text messages and has no work computer "at home or anywhere else". She described the search for documents as "diligent".
"The contempt motion is inappropriate and misleading," she said. "He complied. There are no more documents left to produce by President Trump."
She also derided the James probe as a "political crusade" and "truly a fishing expedition", saying Trump and his companies had turned over more than 6 million documents and paperwork related to 103 Trump entities over an eight-year period.
"We've turned over everything as fast as possible. This is a waste of judicial resources," Habba added.
She also defended Trump's character, saying: "My client is an honest person much to the dismay of certain people in this room".
Trump spokespeople did not immediately respond to a request for comment.
Investigators for James have said in court filings that they uncovered evidence that Trump may have misstated the value of assets like golf courses and skyscrapers on his financial statements for more than a decade.
At the hearing, Assistant Attorney General Andrew Amer said the investigation was being hampered "because we don't have evidence from the person at the top of this organisation".
And he said the failure to turn any documents over at the March 31 deadline to respond to the subpoena was "effectively Mr Trump thumbing his nose at this court's order".
Still, Assistant Attorney General Kevin Wallace signalled the probe was about to move to a new phase, saying: "We plan to bring enforcement action in the near future".
A parallel criminal investigation is being conducted by the Manhattan District Attorney, Alvin Bragg, also a Democrat.
