[5] Gupta served as deputy legal director of the American Civil Liberties Union, where she oversaw its national criminal justice reform efforts.

[21] In 2007, after becoming a staff attorney at the American Civil Liberties Union, Gupta filed a lawsuit against U.S. Immigration and Customs Enforcement (ICE) about detention conditions for children whose parents were asylum seekers.

In this role, she criticized the Trump administration for its response to the Charlottesville Unite the Right rally and accused then-Attorney General Jeff Sessions of trying to increase mass incarceration.

[13] In June 2020, Gupta testified before the Senate Judiciary Committee about the murder of George Floyd and the need to end police brutality in the United States.

[26] During her time at the organization, Gupta worked to combat harmful online misinformation, and "often sat shoulder-to-shoulder with tech leaders including Mark Zuckerberg and Sheryl Sandberg" to discuss content moderation strategies.

[31][32] Gupta's tenure was marked by several high-profile matters, including the investigations of the Ferguson, Baltimore, and Chicago police departments; the appeals of the Texas and North Carolina voter ID cases; the challenge to North Carolina's HB2 law and other LGBTQ2 rights litigation; enforcement of education, land use, hate crimes, and other statutes to combat religious discrimination; the issuance of statements of interest on bail and indigent defense reform, and letters to state and local court judges and administrators on the unlawful imposition of fines and fees in the criminal justice system; and the administration's report on solitary confinement.

In 2016, under Gupta's leadership, the division sued North Carolina, alleging that the state's implementation of House Bill 2 discriminated against transgender individuals in violation of federal civil rights laws.

[33] In August 2016, an investigation by Gupta's division concluded that the Baltimore Police Department engaged in a pattern or practice of conduct that violated the Constitution and federal statutory law, including unconstitutional stops, searches, arrests, excessive force, and enforcement strategies that produced an unjustified disparate impact on African-American residents.

[47] Gupta has said that the Justice Department intends to take a hard line on "killer acquisitions" as part of the Biden administration's effort to rein in monopolies.

[48] She is reportedly responsible for deciding whether Jonathan Kanter, Assistant Attorney General for the Antitrust Division, will be permitted to participate in the United States v. Google LLC case.

[51] In July 2023, Gupta announced a lawsuit against the state of Texas for installing floating barriers in the Rio Grande without federal authorization, saying the devices presented "threats to navigation and public safety and humanitarian concerns".

[57] Over 40 South Asian groups and civil rights organizations have drawn attention to Gupta's role in the University of Farmington scandal.

[58][59] They have called on her to return $6 million in tuition money to South Asian students who they allege were racially targeted and tricked by U.S. Immigration and Customs Enforcement into attending the fake university.

[58][59] Lakshmi Sridaran, executive director of SAALT, alleges that Gupta has the power to immediately return the $6 million paid to DHS, but does not say on what legal basis that is true.