Switzerland's Supreme Court, in a decision made public today, overturned a lower court ruling that would have sent Adamov to the United States.
Adamov was arrested by Swiss authorities in May on an arrest warrant issued by the United States. U.S. justice officials accuse him of diverting up to $9 million in funds intended to improve Russian nuclear security for his private use.
Russia had asked for Adamov to be returned to Moscow, so he could be tried there.
The Russian Foreign Ministry welcomed the ruling, and Adamov's lawyer, Stefan Wehrenberg, said his client was "delighted and satisfied."