"We are committed to improving the online banking experience of our customers, and working with a specialist digital agency will help lead us in that direction," said Terence Khoo, head of UOB's internet channel.
UOB called for a review of its digital communications in July this year.
Commenting on the win, Nick Handel, general manager of Arc, said: "We're delighted to be partnering UOB. The appointment - after an extensive competitive pitch process - is testament to our creativity and continued investment in planning and usability."