JP Morgan, the US investment bank, has bought a new office building in Dublin that can accommodate up to 1,000 staff.
The bank said the purchase reflected its thriving existing business in Dublin, where it employs 500 staff.
However, the new office may provide space for hundreds of JP Morgan workers who it plans to relocate from London following the Brexit decision.
The building, which will be completed next year, is at 200 Capital Dock in Dublin's docklands area.
"Given the momentum of our local businesses, this new building gives us room to grow and some flexibility within the European Union," said Carin Bryans, senior country officer for JP Morgan in Ireland.
Ireland's financial services minister, Eoghan Murphy, said the bank's announcement was a vote of confidence in Dublin's status as a major financial centre.
Earlier this month a senior JP Morgan executive, Daniel Pinto, said up to 1,000 jobs would move from London to Dublin, Frankfurt and Luxembourg before the UK leaves the European Union.
The JP Morgan purchase is the latest development among big banks based in London. Several have said they will need to relocate some operations and staff to other cities in Europe to keep functioning inside the European Union as before.
There is concern that after Brexit the UK's financial services industry could lose its "passporting" rights that allow the businesses to operate throughout the EU.
Standard Chartered has said it is talking to German regulators about making Frankfurt its European headquarters.
Deutsche Bank said in April that it might move up to 4,000 jobs out of the UK as a result of Brexit, which would be nearly half its UK workforce.
Other financial services firms known to be looking at moving some staff out of London include Barclays, Goldman Sachs and the insurance market Lloyds of London.