Former UBS trader Kweku Adoboli was convicted on Tuesday of one count of fraud related to a loss of $2.3 billion.
Adoboli, 32, was a senior trader on the Exchange Traded Funds desk at UBS's investment banking arm in London and had worked for the bank for eight years.
He had denied two charges of fraud by abuse of position and four charges of false accounting.
He bowed his head when the foreman of the jury at Southwark Crown Court gave the unanimous verdict of all 10 jurors.
The judge instructed the jury to keep trying for unanimous verdicts on the other five counts, but said that if they could not reach unanimity he would accept majority verdicts of 9-1.
The jury have now retired again to consider verdicts on the remaining counts.
The charge of which he was found guilty alleged that he dishonestly abused his position by causing losses to UBS of the $2.3 billion, intending to make a gain for himself or cause losses to UBS - or expose the bank to risk of loss - in breach of the 2006 Fraud Act.
Adoboli was arrested in September 2011, and his trial started a year later. - Reuters