He served as an associate at the law firm of Latham & Watkins from 1997 to 1998, leaving to clerk for Judge Susan P. Graber of the United States Court of Appeals for the Ninth Circuit from 1998 to 1999.

He served as an associate at the law firm of Zuckerman Spaeder, LLP from 1999 to 2002, and then as a staff attorney at the Public Defender Service for the District of Columbia from 2002 to 2007.

[15] In July 2019, Mehta sided with the pharmaceutical firms Merck & Co., Eli Lilly and Company, and Amgen Inc. by blocking a Trump administration rule requiring drugmakers to put prices in television ads, a central part of the president's push to lower the cost of prescription medications.

[2] On June 1, 2021, Chief Justice John Roberts appointed Mehta to the United States Foreign Intelligence Surveillance Court.

[1] He is also presiding over three civil lawsuits against Trump and multiple associates, in which several members of Congress and two police officers are suing for damages for physical and emotional injuries they allegedly incurred during the attacks.

On February 18, 2022, Mehta issued a lengthy opinion that rejected Trump's claim of "absolute immunity" from lawsuits, finding that his actions were not part of his presidential duties, and that there was plausible evidence to suggest he engaged in a conspiracy with organized groups to use any means, including violence, to overturn the results of the 2020 election.

The opinion allows the case to proceed, with the plaintiffs demanding documents, depositions, and other evidence from Trump and members of the Oath Keepers and Proud Boys.

Mehta dropped several other co-defendants from the suit, including Rudy Giuliani, Donald Trump Jr., and Representative Mo Brooks.