Health Minister Robin Swann is self-isolating after receiving a close-proximity notification from NI's track and trace app.
He received the notification from the StopCOVID NI app, run by the HSC Public Health Agency.
On Wednesday Mr Swann's UUP colleague John Stewart MLA announced that he had tested positive for coronavirus.
Several other Stormont MLAs posted on social media that they had also received app notifications to isolate.
Writing on Twitter, Mr Swann urged others to download the app.
Mr Swann said he has no symptoms and will only require a test if he develops one of the symptoms of the virus.
An exposure notification from the app means the user has been close to another person who has tested positive.
He is the third member of the Northern Ireland Executive to have to self-isolate in relation to Covid-19.
Communities Minister Carál Ní Chuilín has been self-isolating after a family member tested positive - although she herself has tested negative.
Deputy First Minister Michelle O'Neill has also been self-isolating after a family member tested positive, although she has also tested negative.
She gave her "best wishes" to Mr Swann and acknowledged "self-isolation is difficult for individuals and families," urging people to "play their part in this battle against Covid".
Mr Swann said he will be working from self-isolation for the next 14 days.
He appeared at the Stormont briefing on coronavirus earlier on Wednesday.
We are all in this together.— Robin Swann MLA : #StopCovidNI (@RobinSwannMoH) October 21, 2020
Earlier this evening I received a close proximity notification via our StopCOVID NI App, so I will be working from self isolation for the next 14 days.
Download #StopCovidNI help break the infection chain...
UUP MLA John Stewart confirmed in a tweet on Wednesday evening that he had tested positive for coronavirus.
"Felt really unwell Monday, booked test Tuesday and result today," he tweeted.
The East Antrim MLA said he had felt ill and had suffered headache symptoms as well as fatigue, before booking a test.
Mr Stewart said he had completed the track and trace procedure and had logged his diagnosis through the app.
Sadly I have tested positive for Covid-19 today.— John Stewart MLA (@JohnStewart1983) October 21, 2020
Felt really unwell Monday, booked test Tuesday & result today. Very fast & efficient.
Feeling ill, head pounding & really fatigued... 😔
Have completed track & trace / StopCOVIDNI App & now self isolating. #InThisTogether
On Wednesday evening, a party spokesperson confirmed fellow UUP MLA Andy Allen had received an exposure notification from the app and would have to isolate for 14 days.
The DUP's Pam Cameron also confirmed she was self-isolating after receiving a notification, tweeting a screengrab of the app.
The South Antrim MLA is the deputy chairperson of the Stormont health committee.
Responding to Ms Cameron, independent MLA Trevor Lunn said he was also self-isolating, and was on his fourth day of doing so.