The owners - the Duckworth family of Lancashire - offered the community first refusal to buy and a deal is due to be signed and sealed within the next few weeks.
The family have used the estate since the 1920s and usually only stay on the island for the salmon season.
In total, 142 backed the purchase of the island with 37 against.
The community trust received £100,000 from the Scotland Land Fund - financed by Scottish Government - to help purchase the 2,260 hectares of the Great Bernera Estate including 69 crofts around Kirkibost, Tobson, Hacklete, Breaclete and Croir.
Both residents and thousands of complete strangers - aided by a £1m anonymous donation - pitched into secure the Hebridean isle from German artist Professor Murama.
The population has since risen from around 65 to more than 100 with eight pupils now at the school, including one in nursery.
The island has the first completely wind, water and sun-powered electricity grid in the world.
Ideas to boost the island economy range from a new four-star hotel to a campervan site, renewable energy development and a pier at Kirkbost.
The purchase of Great Bernera, which has yet to be completed, will close a powerful chapter in Scotland’s history of land ownership.
GIGHAPopulation 170Gigha, off the west coast of Kintyre, was put up for sale by businessman Derek Holt - former owner of Skibo Castle - in 2001 and was bought by islanders for £4m raised by the Scottish Land Fund and Highlands and Islands Enterprise.