The council will provide nearly £160,000 to bridge the gap between the cost of the project, and funding secured by the Isle of Gigha Heritage Trust from the Scottish Government and other sources.
The project will deliver five new affordable houses, to support both older and younger island residents.
They are intended to help young people stay and work on the island and so protect its future; and to make it easier for older residents to continue living on Gigha as their health demands change.
Overall costs include the construction of the houses as well as the high costs of delivering island infrastructure needed to support the new homes.
Councillor Robin Currie, policy lead for economy and rural growth, said: “Developing housing options across the area is a priority for the council. To attract and retain the people and skills we all need in Argyll and Bute, there has to be a range of homes on offer.