Switzerland's Federal Criminal Court said it had confirmed a settlement between 54-year-old computer technician Lutz Otte and the public prosecutor, in which he agreed to plead guilty in return for the three-year sentence, half of which was suspended.
Otte, a German citizen who began working as a contractor for the Zurich-based bank in 2005, admitted that he had gathered information about the bank's clients, including their names, addresses and account numbers, between October and December 2011.
He had then compiled a list of German clients with assets of more than 100,000 euros, Swiss francs, British pounds or dollars, and passed it on to a retired German tax inspector.
In exchange, he had been set to receive €1.1 million euros, although he had only received part of that amount by the time he was caught.
He told the court he had planned to use part of his compensation to pay off his own back-tax debt to German authorities.
Julius Bär declined to comment on the verdict.