More than 30 staff at Hillsborough Castle in County Down are to be made redundant.
The 100-acre site is run by Historic Royal Palaces and is the official NI residence of the Queen.
The charity said that like many tourist attractions, it had been badly affected by the coronavirus pandemic.
Thirty-three full-time posts are to go and Historic Royal Palaces has started a consultation process, having “exhausted all other options”.
It said it regretted making the redundancies, but needed to act to sustain its long-term future.
Hillsborough Castle reopened to the public in 2019 following a £24m refurbishment, which took five years.
However, the venue had to close during lockdown, which it said had led to a significant shortfall in its finances.
While the charity had furloughed staff, it said it was now eating into its reserves and expected to exhaust those by the end of the year.
The head of Hillsborough Castle, Laura McCorry, said the downturn in visitors and international tourism had been devastating.
“This is a difficult time for the tourism industry and we are determined to play our part in its recovery,” she said.
“It is a matter of enormous regret that we can only do so if we act now to reduce our payroll costs and make the castle financially sustainable.”