The 26 year old man was tested for the virus in a Garda station in north Dublin last Friday, as he was showing symptoms.
He was then brought to Cloverhill Prison in Dublin, which currently has 333 inmates.
Though it has only now emerged that the man’s test was positive, he had been placed in quarantine since arriving at the jail and has not mixed with other prisoners.
Staff have used personal protective equipment at all times when dealing with the prisoner.
Last week, a 23 year old woman in the Dochas Women's Prison became the first prisoner in Ireland to test positive for the virus.
