McGowan, 45, was fined $2,500 and given a 12-month suspended sentence at a courthouse in Virginia two years after cocaine was found in a wallet she left behind at Dulles International Airport, WTOP-FM reported.
The actress, one of the first women to accuse disgraced Hollywood producer Harvey Weinstein of sexual assault, told the news station she "just wanted it to be over, however it ended."
McGowan was initially charged with a felony that could have carried jail time, but the plea deal reduced the charge to a misdemeanor.
Her lawyers last year suggested the drugs were planted in retaliation for her accusations against 66-year-old Weinstein. No evidence was presented to back up the claim.
The "Charmed" star's lawyers instead argued that several hours elapsed between the time McGowan left the plane and the time the drugs were found by a cleaning crew in the first-class section of a United Airlines cabin. They said it was impossible to account for who may have handled the wallet during that time.
Paul Ebert, prosecutor for Prince William County, said McGowan was treated like anyone else in this type of situation.
“She had no record,” Ebert told WTOP. “She smuggled a small amount of cocaine. She’s treated like everyone else, irrespective of what she is or who she is.”
The Associated Press contributed to this report.