The Elliot Group says it was made aware this morning by a sub-contractor that a worker had the virus.
The site in South Great George Street will undergo a deep clean tomorrow, and the developer is waiting for further instructions from the HSE.
All workers have been told to undergo testing for Covid-19.
This follows the closing of two construction sites earlier this week, one on Townsend Street and one in Grangegorman, as workers there also tested positive for the virus.
