Alice has more than paid her debt to society by serving over 21 years of a life-without-parole sentence as a nonviolent drug offender.
Kardashian West joined what has been a long-running campaign for Johnson's freedom, spearheaded by the clemency foundation CAN-DO, friends and family.
Ms Johnson's commutation of sentence is the sixth act of clemency granted by Mr Trump since he took office and the second one issued after a celebrity had appealed to him. "Telling her for the first time and hearing her screams while crying together is a moment I will never forget", she said in the tweet. "Because there are so many, as you've said, like me, who need to have the opportunity that I've had", she told GMA's Michael Strahan.
Michael Scholl, a member of Johnson's legal team, said she was released just before 6 p.m. from federal prison in Aliceville, Alabama.
The White House said in a statement that Johnson "has accepted responsibility for her past behavior".
"I think that she really deserves a second chance at life", Kardashian told news reporters. Why was Alice Johnson jailed?More news: Eagles players individually decided on WH trip
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Trump has also pardoned conservative author and filmmaker Dinesh D'Souza, Arizona sheriff Joe Arpaio, former Vice President Dick Cheney's chief of staff I. Lewis "Scooter" Libby and Kristian Saucier, a Navy sailor.
Johnson's supporters argued she should not have to spend the rest of her life in prison for a nonviolent drug offense.
Kim Kardashian West broke her silence about her visit to the White House to obtain a commutation for Alice Johnson from the president, and she fired back at her critics. In a Twitter statement, Kardashian said, "I would like to thank President Trump for his time this afternoon".
Ivanka Trump was one of the first people she called to plead Johnson's case, Kardashian said. She was convicted for facilitating communications in a cocaine trafficking operation in Memphis, Tennessee and was given a life sentence without the possibility of parole. Johnson said she wanted to thank the president for giving her "another chance" at life.
She was set free after Kim Kardashian West went to the White House to ask the president to commute her sentence.