The moviemaker was sentenced to a year behind bars in 2010 after pleading guilty to two counts of making false statements to Federal Bureau of Investigation (Fbi) officers who were probing jailed Hollywood private detective Anthony Pellicano.
He then attempted to withdraw the plea as he appealed the case, but the review was rejected last August (12) - and on Wednesday (03Apr13), he surrendered to start his stint in jail.
The star was taken to a federal prison in North Dakota, according to The Hollywood Reporter. As well as his jail sentence, he faces three years of supervised release and was ordered to pay a $100,000 (£62,500) fine.
MCTiernan initially admitted to hiring Pellicano to illegally record movie producer Charles Roven's phone conversations and lying to authorities about it. He was also convicted on one count of perjury for lying to a federal judge during the period when he wanted to withdraw his earlier guilty plea, and his wife Gail is convinced the punishment was too severe.
She tells The Hollywood Reporter, "There was only one false statement. He said he had hired Pellicano only one time. Actually he hired him twice. And he said that to a stranger over the phone. Hardly something deserving of a year in prison, a $100,000 fine and seven years of harassment, in my humble opinion."