Agriculture Minister Edwin Poots is self-isolating after testing positive for Covid-19.
The DUP assembly member was tested twice while in hospital for an operation to remove his appendix.
One test was negative, while another had a positive result for coronavirus.
The DUP said Mr Poots has not displayed any symptoms but is self-isolating until Wednesday.
He is the first Stormont minister to have a positive test for Covid-19.
A DUP spokesman said: "Mr Poots was tested twice whilst in hospital for an appendix operation.
"One test was a negative result and the other showed a positive result for Covid-19. So far, Mr Poots has not displayed any symptoms but is isolating until 16 December."
The Lagan Valley MLA was taken to hospital on December 6 for emergency surgery on his appendix, it was reported last week.
He later posted a photo of himself on Twitter and thanked hospital staff who had taken care of him.
Two other MLAs - the SDLP's Daniel McCrossan and the UUP's John Stewart - have previously tested positive for coronavirus since the pandemic began.
