Jasveen Sangha pleaded guilty to five federal charges, including providing the ketamine that led to Perry's death.
Her trial had been planned to start later this month.
She is the fifth and final defendant charged in Perry's overdose death to admit guilt.
Prosecutors had cast Sangha, a 42-year-old citizen of the United States and the United Kingdom, as a prolific drug dealer who was known to her customers as the "Ketamine Queen," using the term often in press releases and court documents.
Making good on a deal she signed on August 18, Sangha pleaded guilty to one count of maintaining a drug-involved premises, three counts of distribution of ketamine and one count of distribution of ketamine resulting in death.
Prosecutors agreed to drop three other counts related to the distribution of ketamine and one count of distribution of methamphetamine that was unrelated to the Perry case.
The final plea deal came a year after federal prosecutors announced that five people had been charged in Perry's October 28, 2023 death after a sweeping investigation.
A judge will schedule sentencing for Sangha.
She could get up to 65 years in prison.
The judge is not bound to follow any terms of the plea agreement but prosecutors said in the document that they will ask for less than the maximum.
None of the co-defendants have been sentenced yet.
Sangha and Dr Salvador Plasencia, who pleaded guilty in July, had been the primary targets of the investigation.
Three other defendants - Dr Mark Chavez, Kenneth Iwamasa and Erik Fleming - pleaded guilty in exchange for their co-operation, which included statements implicating Sangha and Plasencia.
Perry was found dead in his Los Angeles home by Iwamasa, his assistant.
The medical examiner ruled that ketamine, typically used as a surgical anesthetic, was the primary cause of death.
Sangha presented a posh lifestyle on Instagram, with photos of herself with the rich and famous in cities around the globe.
Prosecutors said she privately presented herself as a dealer who sold to the same kind of high-class customers.
Perry had been using ketamine through his regular doctor as a legal but off-label treatment for depression, which has become increasingly common.
Perry, 54, sought more ketamine than his doctor would give him, and his search for more led him to Sangha through his friend Fleming about two weeks before his death, prosecutors said.
Fleming messaged Perry's assistant saying her ketamine was "amazing" and that she deals only "with high end and celebs".
Perry bought large amounts of ketamine from Sangha, including 25 vials for $US6,000 ($A9,154) in cash four days before his death, prosecutors said.
On the day of Perry's death, Sangha told Fleming they should delete all the messages they had sent each other, according to her indictment.
Sangha has been in federal custody for about a year.
Perry struggled with addiction for many years, dating back to his time on Friends, when he became one of the biggest stars of his generation as Chandler Bing.
He starred alongside Jennifer Aniston, Courteney Cox, Lisa Kudrow, Matt LeBlanc and David Schwimmer for 10 seasons from 1994 to 2004 on NBC's megahit series.
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