The Kings Highway between Braidwood and the South Coast was reopened on Tuesday afternoon, weeks ahead of schedule.
The road has been closed since December due to Currowan and Clyde Mountain fires that have devastated the area. It reopened about 2pm.
It will be a welcome boost for businesses at the South Coast who have reportedly lost thousands of dollars in trade as the road is the main thoroughfare to and from Canberra.
It was previously expected the highway could be closed until late-January or early February. NSW Deputy Premier John Barilaro indicated in late-December the highway could have been closed for at least month.
Up to 70 transport workers a day have been working on reopening the stretch of road since Monday January 6.
About 1200 hazardous trees have been removed on the 43-kilometre section of the highway. Also, 43 damaged guardrails and 500 cats eye reflector lights have been repaired.
Member for Bega Andrew Constance announced the re-opening on Tuesday morning. He said it was welcome news to locals.
"The Kings Highway is an essential route in and out of the South Coast and our number one priority remains ensuring the safety of the community and all involved in the recovery efforts," Mr Constance said.
Eurobodalla mayor Liz Innes said the highway re-opening would be a major boost for the area.
"Bushfires have devastated our community and our landscape, and we're hurting," Ms Innes said.
"Part of our recovery is the return of visitors and particularly our Canberra friends to help local businesses get back on their feet."
It comes as areas in the South Coast not directly impacted by the bushfires were declared re-opened for business after an assessment meeting by the NSW Police, NSW Rural Fire Service, Transport NSW and local councils on Saturday.
A roundtable meeting will also be held with small business groups will be held at Parliament House on Tuesday to determine the best way forward for small businesses affected by the fires.
Conditions have eased at the major firegrounds on the South Coast. Both the Currowan and Clyde Mountain fires are "being controlled", according to the NSW RFS.
Further south, the Badja Forest and Werri Berri fires in the Bega Valley are also "being controlled". The Border Fire, burning near Eden, remains "out of control".
Rainfall of up to 50mm is forecast for south-east Australia this week.