A programme of varied activities was arranged for the opening on Wednesday, including demonstrations of various water sports by school children and also a guided tour of the marina.
The new marina boasts 53 new pontoons. Over half of the berths have already been allocated, with officials confident that the rest of the berths will be allocated soon.
Dumfries and Galloway Council have been working in partnership with Scottish Enterprise to provide the new marina for Stranraer.
The completion of the marina is one of the key aspects of the Stranraer Waterfront Regeneration. Work is on-going on other projects that aim to reposition Stranraer and Loch Ryan as a distinctive and successful marine leisure destination.
Cllr Roger Grant, Chair of the Planning, Housing and Environment Committee, said: "I am delighted that Stranraer Harbour's new marina is now open.
"This opening event is an opportunity for us to celebrate the completion of a key milestone. The marina is a fantastic facility. I am confident that it will encourage visitors from outside the region to come and visit Dumfries and Galloway."