Royal Bank of Scotland's chief executive Ross McEwan has issued a memo to staff, warning that the vote to leave the EU has created "short, medium and long-term" economic uncertainties.
Mr McEwan also moved to reassure employees that RBS is well placed to deal with the fallout.
"We had planned extensively for both possible outcomes to ensure we were well placed to support our customers and colleagues," Mr McEwan said.
"The result of the vote carries with it a range of unknowns about the short, medium and long-term prospects for the UK and its economy. Added to this, we now have a period of political uncertainty," he added.
RBS's share price has taken a pummelling since the vote - falling to its lowest level since the financial crisis yesterday, before rebounding today.
Royal Bank of Scotland owns Ulster Bank here.
New Zealand born Mr McEwan also gave a nod to the bank's international workforce, amid fears that Britain could lose access to the single market.
"As someone born outside the UK, I see one of this country's biggest strengths as its openness to the rest of the world, and the people of it. As a major employer and backer of the economy, we have a duty to ensure that we reflect that," he stated.
"The diversity of those who make up this bank at every level is key to our success. In uncertain times I want to ensure that everyone understands that," he added.