Incumbent Labour MP Clare Curran had her majority slashed in the traditional Labour stronghold of Dunedin South and National pulled off an upset by winning the party vote in the working class electorate.
The result left both sides claiming victory, with Ms Curran declaring the result showed Dunedin South remained a "pretty strong"
Labour seat. National rival Joanne Hayes described the result as "beyond my wildest dreams".
Ms Curran polled 15,759 votes, 3867 clear of National rival Joanne Hayes.
However, the winning margin is markedly down on her 6449-vote majority in 2008.
And, in a reversal of 2008, National won the party vote, polling 13,190 to Labour's 11,429. Three years ago Labour got 17,408 party votes and National 12,742.
Ms Curran, celebrating with about 50 campaign volunteers and supporters at Robbie's Bar and Bistro in South Dunedin, said voters sent a "clear message" they wanted the seat to remain with Labour.
The increased party vote for National mirrored results around New Zealand, she said.
Ms Hayes, celebrating with about 100 volunteers and supporters at The Kensington pub, admitted she was surprised to have closed the gap with Ms Curran and win the party vote.
"It's beyond my wildest dreams."
National list MP Michael Woodhouse, who polled second in Dunedin North, said he was "absolutely delighted" with results there, as well as those in Dunedin South, and attributed it to National's "energetic, visionary and positive" campaign.
"I think we can be very pleased."
Labour's Dr David Clark won Dunedin North with a 3304 majority, retaining the seat for Labour.
Mr Woodhouse rang Dr Clark's campaign team in Alhambra rugby clubrooms at 10.05pm to concede.
Dr Clark thanked his supporters, and retired Labour MP Pete Hodgson, who left the seat in "good heart".
Mr Hodgson never took the grassroots movement in Dunedin North for granted, and that meant the campaign had "stood on the shoulders of giants", Dr Clark said.
The win was a culmination of 12 months' hard work from dedicated volunteers.
His brother, Ben Clark, contested North Shore for Labour, which National's Maggie Barry took with a huge majority.
Dr Clark's mother, Faye, was in Dunedin to support him, while father Richard was in Auckland. That both sons were contesting seats had been a surprise for his parents, who were interested in "social justice" but were not party political.
Dr Clark said he and wife, Katrina Lynn, who have a young son, would ensure they had appropriate strategies in place to deal with him dividing his time between Wellington and Dunedin.
Asked about Labour's reduced party vote majority of 587 in Dunedin North, Dr Clark said the Greens had run a strong campaign in the electorate, winning 5829 party votes.
Dr Clark's majority was also down on Mr Hodgson's 7155 in 2008.
Mr Woodhouse said he was impressed with the party vote result in Dunedon North, which saw National poll within 587 votes of Labour.
"That was 5000 three years ago. I think we can be very pleased."
While supporters heartily congratulated their new MP, the mood in the Labour Dunedin North headquarters was subdued due to Labour's national result.
At the Greens' Dunedin base at The Church, the mood was much more jubilant, with a delighted Dunedin South candidate Shane Gallagher pleased with their increased party vote share in Dunedin.
Greens co-leader Metiria Turei Skyped to congratulate Dunedin party members and Mr Gallagher on an excellent campaign.
Mr Woodhouse received 8233 candidate votes, with National getting 8276 party votes.
Incumbent Bill English held Clutha-Southland with a whopping 14,915 majority over Labour's Tat Loo. National won the party vote with 18,427 compared to 4710 for Labour.
Addressing a 200-strong gathering at the Jacks Point Clubhouse in Queenstown, Mr English joked that Winston Peters had texted asking for a job in Cabinet. He said he had texted back a simple reply: 'No'.
He said he had spoken to John Key and the national result "was better than we expected".
In Te Tai Tonga, Labour's Rino Tirikatene (5868) beat Rahui Katene (4423) of the Maori Party.
Maori Party leader Tariana Turia said it appeared the electorate was sending the Maori Party a message.
"And it may well be ... that they haven't liked the relationship with National," she told TV3.
"I think the really disappointing thing for me is that Rahui Katene has worked harder than any Te Tai Tonga member that I can think of."