The completion marks the first anniversary of the construction of a forest track which laid the foundation for the link.
Residents previously had to walk or use off-road vehicles to reach opposite ends of the four mile-long (6km) isle.
Kerrera, which sits to the west of Oban Bay, is home to around 70 people, but about half of them have been cut off from the CalMac ferry service in the centre of the island at Gallanach.
Those in the north of have faced a walk – or quad bike trip – over bog or rough forest track to catch the 15-minute ferry to Oban or self-organised transport.
The islanders campaigned for decades for a proper road across the island, citing emergencies, tourism spend and convenience as key drivers.
After demand grew over the previous half-century it was relatively swift work to carry out following the arrival of earth moving machinery by ferry.
In a few short months, Alistair McCrae and his team from Barrachander Quarry in Taynuilt had completed the forestry grade track from the ferry in the centre of the island, up to Ardentrive Farm in the north on behalf of the Isle of Kerrera Development Trust (IKDT).
At the time, Project Manager, islander Martin Shields was delighted to see Stage One complete.
He said: “The people in the north of the island have always had a struggle on their hands to get on and off the island. There is a fantastic marina in the north where residents can keep their boats on the water, but you wouldn’t want to have to rely on them as your lifeline.”
"I don’t know how many meetings myself and my fellow board members have attended over the years. In spite of this, I’ve always felt that we needed to keep believing, to keep getting people round the table because sooner or later, it will land on the desk of someone able to unlock the funding to make it happen.”
Mr Shields said the new road would also allow Kerrera to build a resilience plan to insure residents had the best access possible to emergency services, schooling, shops and other vital services in Oban and would bring an end to people “walking in the dark for miles carrying their groceries back home.”
The Scottish government provided £500,000 towards the first stage while tarring the route received £200,000 of Crown Estates Coastal Communities funding and a private donation of £50,000.
It is anticipated the road itself will attract visitors who are drawn to Kerrera for its walking routes, history and wildlife including native goats, ravens and seabirds.
Gylen Castle was built at the southern end of the island in 1582 by the Clan MacDougall and was left in ruins following a siege in 1647.
Celebrating the road’s completion, Mr Shields continued: "The whole of the island has access to the marina now, and families can mix and get together for things like a Halloween party this weekend.
"This is the first major surfacing works that has ever happened."