Stena Line will invest up to £200m ($315m) in a new relocated ferry port facility at Loch Ryan, Scotland.
The Scottish Government has recently announced the port relocation from Stranraer to the mouth of Loch Ryan.
The investment includes the addition of two large modern ferries when the port becomes fully operational on its Irish Sea service to Belfast Port.
Construction work at the 28-acre port is expected to take about 20 months, which will be completed by autumn 2011.
In 2008, the Irish Sea ferry operator opened a £37m ($58m) port facility in Belfast harbour.