Saturday's election results saw Ms Curran's majority nearly halved to 3867, with 15,759 votes compared with National rival Joanne Hayes' 11,892, well down on her 6449-vote majority in the 2008 election.
That was also a dramatic turnaround from 2005, when former Labour incumbent David Benson-Pope enjoyed an almost 10,000-vote majority.
However, the real shock came in the Dunedin South party vote, where National polled 13,190 votes to Labour's 11,429.
The results left both sides claiming victory, with Ms Curran declaring the result showed Dunedin South remained a "pretty strong" Labour seat, while National rival Joanne Hayes described the result as "beyond my wildest dreams".
Ms Curran, celebrating with about 50 campaign volunteers and supporters at Robbie's Bar and Bistro in South Dunedin, said Dunedin South voters sent a "clear message" they wanted the seat to remain with Labour.
The party vote was a different situation, and she said she could not yet explain the result.
"I don't know the answer. I think it's probably best to have a bit of a think about that and for the party to analyse what the implications are," she said.
She praised the efforts of her team of volunteers and supporters for the "grass roots" campaign.
Mrs Hayes, celebrating with about 100 volunteers and supporters at the nearby Kensington pub, was both ecstatic and "surprised" by the result.
She had aimed to run a "really strong" party vote campaign, and try to halve Ms Curran's electorate majority, and Saturday's results left her claiming victory on both counts.
At 64 on the National Party list, Mrs Hayes - a consultant in the health sector - missed out on a seat in Parliament.
Green Party candidate Shane Gallagher took third place in the electorate, with 2852 votes, while the party earned 4313 votes.
