Gian Gisler allegedly opened and managed more than 60 hidden accounts on behalf of over 38 US taxpaying clients, the Justice Department said.
Beginning in the mid-1990s, Gisler was a client adviser at UBS until late 2008, when a US investigation into UBS became public and he then began working for a Swiss asset management firm, according to prosecutors.
They also said Gisler took money from clients who wanted their funds to remain undeclared and provided it to other UBS clients so that no cash crossed the border.
If convicted of conspiracy, Gisler, who currently lives in Zurich, Switzerland, could be sentenced to up to five years in prison and a fine of up to $250,000.
In 2009, UBS admitted to US tax fraud and identified some 300 clients suspected of tax fraud to authorities.