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Tim Wu will take a sabbatical from Columbia Law School.Credit Anthony Lanzilote for The New York Times

Tim Wu, the influential law professor and former candidate for lieutenant governor, is joining the office of the New York State attorney general, Eric T. Schneiderman.

Mr. Wu’s appointment brings a well-known figure in technology circles to Mr. Schneiderman’s office, which has sought to assert itself as a watchdog over technology companies and the so-called sharing economy.

Mr. Wu, who starts his job on Monday, will serve as a senior lawyer and special adviser to Mr. Schneiderman, the attorney general’s office said. He will be on sabbatical from Columbia Law School, where he is a professor.

“If I have a life mission, it is to fight bullies,” Mr. Wu, 43, said in an interview. “I like standing up for the little guy, and I think that’s what the state A.G.’s office does.”

Mr. Wu will focus on issues involving technology, including protecting consumers and ensuring fair competition among companies that do business online, the attorney general’s office said.

“Tim provides an unparalleled depth of understanding of the intersection between technology and the law,” Mr. Schneiderman, a Democrat, said in a statement. “His expertise in how legal rules can facilitate competition in modern markets is broad and deep, as is his commitment to justice and fairness.”

Mr. Schneiderman has pursued matters involving a number of technology companies during his time as attorney general, including Airbnb and Lyft. He has also pushed smartphone makers to better deter theft.

In an Op-Ed article last year in The New York Times, Mr. Schneiderman wrote that the online world “offers great promise but is also becoming one of the primary crime scenes of the 21st century.”

“Just because a company has an app instead of a storefront doesn’t mean consumer protection laws don’t apply,” Mr. Schneiderman wrote.

Mr. Wu is known for coining the phrase “net neutrality,” and has written about subjects including antitrust and copyright issues. He also served as a senior adviser at the Federal Trade Commission.

Last year, Mr. Wu became an unexpected player in New York’s political world, running for the Democratic nomination for lieutenant governor as part of an effort to give disaffected liberals an alternative to Gov. Andrew M. Cuomo, a Democrat.

Mr. Wu was the running mate of Zephyr Teachout, a fellow law professor who mounted a surprisingly potent challenge against Mr. Cuomo, though the governor still prevailed. Mr. Wu won about 40 percent of the vote against Kathy Hochul, a former congresswoman who is now the lieutenant governor.

Mr. Cuomo has long had a notably frosty relationship with Mr. Schneiderman, who is a possible candidate for governor in 2018.

But in recent months, as Mr. Cuomo has feuded with Mayor Bill de Blasio, Mr. Cuomo has seemed less hostile to Mr. Schneiderman. He appointed the attorney general to serve as a special prosecutor for police-related civilian deaths, and Mr. Schneiderman accompanied the governor on a trip last week to Puerto Rico.

Mr. Wu said his hiring was not a case of Mr. Schneiderman wanting to recruit an antagonist of the governor’s.

“This is not about politics at all; it’s about substance,” he said. “I believe strongly in the work the A.G.’s doing and that’s why I joined up, not for any other reasons.”

The attorney general’s office said Mr. Wu will continue to be paid by Columbia, and will not receive a state salary. In the interview, he said that “the states are where the action is” in areas like antitrust enforcement.

“I’m interested in working on pocketbook issues where consumers can feel it, where the new economy makes them nervous and where you want the government to be carefully watching companies who could be abusing customers,” he said.