Svetlana Bakhmina, the former deputy head of the legal department at the oil company's Yukos Moskva unit, had maintained her innocence since she was arrested in 2004. Bakhmina, who has two children, is pregnant and is due to give birth in December.
"My client has filed a pardon petition in which she pleads guilty," Roman Golovkin said.
In September, a court turned down her request for parole despite her pregnancy and certificate of good prison conduct. It was the second such rejection by the court in Central Russia, where Bakhmina has been serving a 6 1/2-year sentence since October 2006.
Decisions to pardon convicts are made by the president.
Bakhmina was charged with failing to pay 606,000 rubles ($22,600) in taxes in 2001-2002 and of diverting 8 billion rubles' worth ($298.73 million) of property from Yukos subsidiary Tomskneft in the late 1990s.
Legal proceedings launched against Yukos in 2003, seen by many as politically motivated, resulted in the conviction of Bakhmina and other executives and shareholders of what was Russia's largest oil producer, including founder and then-CEO Mikhail Khodorkovsky.
