More than 170 landline telephones have been installed in cells at Castlerea prison.
It's hoped the initiative will allow inmates to maintain family relations and in turn help rehabilitation.
While the telephone handsets cost just 16 euro each, the associated equipment amounted to 152,104 euro.
According to the Irish Times, Inmates will only be allowed to make outgoing calls with the possibility of a dial in system being considered in the future.
The project has been rolled out at several other prisons including Cloverhill, Limerick and Portlaoise at an overall cost of all almost one million euro.