[3] On January 27, 1998, Berzon was nominated by Bill Clinton to the Ninth Circuit for the seat vacated when John T. Noonan assumed senior status on December 27, 1996.

[3] On February 10, 2003, Berzon dissented from denial of en banc after a panel rejected a Washington State Patrol cadet's claim that he was forced to resign due to lack of religious accommodations.

[8] Also in 2009, Berzon dissented in Abebe v. Holder, an immigration case by a lawful permanent resident seeking protection for deportation.

Berzon, joined by several other liberal judges, argued that allowing the deportation of Abebe violates equal protection.

[10] In October 2014, Berzon joined an opinion that held same sex marriage bans in Idaho and Nevada violated the U.S. Constitution.

[13] On April 9, 2018, in Rizo v. Yovino, Berzon joined the opinion of Stephen Reinhardt that said prior pay may not be considered for deciding one's salary, under the Equal Protection Act, due to the gender wage gap.

Berzon wrote in a concurrence that the immigrant had shown proof of harm, but she was upset that the court did not mention 5th Amendment rights.

Richard Paez wrote a similar concurrence also saying that illegal immigrants were entitled to due process under the 5th Amendment, which Berzon and William A. Fletcher joined.

[17][18] In Ceren v. Barr, decided on March 5, 2020, Berzon dissented, arguing that the Immigration Judge abused their discretion by refusing to allow the defendant's attorney, who was ill, to finish her closing arguments.

[20][21] Although Berzon voted to largely bar a lawsuit against big tech companies arguing that they are responsible for a terror attack, she called for the Court to take the case en banc to reconsider precedent that protects such algorithms from Section 230 liability.

Berzon wrote a 44-page concurring opinion in Duncan v. Bonta, a major 2nd amendment case challenging a law that limits gun magazine capacity to 10 bullets.

Berzon explained that small sample sizes often create an issue in experiments that judges cite to argue their point, and citing Daniel Kahneman, she explained that "Sample size issues and the drive to draw a single legal conclusion are not the only potential methodological pitfalls for the “text, history, and tradition” test.

According to Berzon, the decision "allows a single judge to enjoin potential plaintiffs from filing any sort of lawsuit if the judge predicts that the lawsuits will fail upon a defense grounded in a federal right" and will severely limit enforcement of California's Proposition 65, which aims to reduce toxic chemicals in drinking water.