Destination Queenstown was invited to join the Southern Scenic Route Steering Group by regional members of the group and DQ chief executive Tony Everitt believed it would provide another strong attraction for visitors.
The route was previously a 440km half-loop between Dunedin and Te Anau, snaking through Balclutha, the Catlins, Invercargill, Bluff, Riverton and Tuatapere.
It will now run 601km in total, adding the townships of Mossburn, Five Rivers, Athol, Garston and Kingston on its way to Queenstown.
"By providing visitors with an international airport at each end of the route, in Queenstown and Dunedin, it's even easier for visitors," he said.
"The Southern Scenic Route allows our international visitors a chance to explore on their own, to find hidden lakes and side roads, to meet local characters and experience southern hospitality - to find the real New Zealand."
The brainchild of Tuatapere residents John Fraser and Les Hutchins, the route was originally planned to stretch between Queenstown and Dunedin.
However, the full route was deemed "a logistical nightmare", and a shortened route was officially opened in 1988.