The Wolverhampton-based company has acquired a site on the Shawfair Park facility that is being developed by the Buccleuch Property group, owned by the eponymous duke.
The price of the deal has not been disclosed. Marston's is finalising plans for the new outlet.
With around 2150 pubs and bars across England and Wales, Marston's is also building a pub near Dunbar, East Lothian.This is due to open in April next year.
Marston's acquisitions manager, Adrian Blackburn, said: "This is an exciting and welcome acquisition for the company as it marks our entry into this region along with our proposal on the A1 at Dunbar."
A spokeman added that Marston's plans to open outlets in five locations in Scotland next year.
Sandy Smith, development director of Buccleuch Property, said the sale was a milestone in the development of the 35-acre Shawfair Park scheme, which is next to Edinburgh City Bypass and near Dalkieth.
The group is developing a business park on the site that will become the commercial hub for south Edinburgh and Midlothian.