UBS made a pre-tax profit of 1.2bn Swiss francs (£722.9m) in the three months to 31 December.
This compares with a loss of 9.58bn francs in the same period in 2008.
Its annual net loss was reduced to 2.7bn Swiss francs last year – with the damage limited by the strong performance
at the close of the year.
However, clients withdrew more money than forecast, the figures showed.
The return to profit in the final quarter of 2009 was also helped by a tax credit worth 480m francs.
In a letter to shareholders, chief executive Oswald Gruebel said: "We entered 2009 at the height of the crisis. By the end of 2009 UBS has returned to profitability, delivering on its priorities.
"We expect that our return to profitability will increase clients' confidence in UBS and restore our reputation."