The 62-year-old was released after more than two years behind bars following a successful parole bid.
"I'm very happy to be out. It's a beautiful day to be free," he said, speaking to media from a car on his way out of Canberra's Alexander Maconochie Centre on Thursday.
The former army lawyer was sentenced to a maximum of five years and eight months in jail in May 2024 after he helped steal secret defence documents about the Afghanistan war. He then leaked them to the media.
McBride aimed to expose intense investigation of Australian soldiers in Afghanistan, but it was revealed soon after that defence personnel had been involved in illegal killings while on the front lines. He pleaded guilty to three charges, including theft.
"I'm looking forward to seeing my dog and my daughters ... hopefully my dog will remember who I am," he said upon release.
He declined to answer questions about Australia's whistleblower laws, saying he wanted to be fair to Attorney-General Michelle Rowland, who had just approved his parole.
McBride will be allowed to serve the last three years of his sentence in the community under supervision and strict conditions.
Ms Rowland granted the parole early on Thursday morning, a department spokesperson confirmed to AAP.
"The government does not provide specific commentary or details about individual parole matters," the spokesperson said.
McBride served his full non-parole period of 27 months and was granted release the same morning he became eligible for it.
He had been brave in exposing war crimes, Whistleblower Justice Fund founder and former senator Rex Patrick said.
"It's so good to see the end of an awful saga that should never have happened. I salute David who walks away from prison with his head held high," he said.
The news was also celebrated by Greens senator David Shoebridge, who said McBride should have walked free long ago.
"My friend David McBride has paid a terrible price for saying the truth. It's a price no whistleblower should ever be made to pay again," Senator Shoebridge said in a statement.
An ACT government spokesperson said the territory's corrective services would continue to perform its statutory functions, which included monitoring McBride when he was in community.
The father of two also confirmed he was battling lung cancer and was due to undergo an operation in a couple of weeks.
"Hopefully that will clear it (the cancer) out," McBride said.
The whistleblower said prison had been a "hard but good" experience, for which he praised prison staff.
"The corrective services were very professional, very polite to me, and the prisoners were good too. It was on the whole a very positive experience. I'm happy to be out though."
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