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With 100% of the vote counted, Mr Walker topped the poll with 19,524 votes, comfortably ahead of Labour candidate Cherie Chapman on 6519.
Wakatipu National Party Chairman Mark Wilson, of Queenstown, said he was proud to introduce Mr Walker as the new sitting MP.
Mr Walker asked his partner Penny Tipu to join him as he addressed about 70 people at his election night party - at Lone Star on Brecon Street, Queenstown.
He told the cheering crowd he couldn't have attempted or succeeded on the campaign trail without her support - or driving ability.
Speaking to the Otago Daily Times after the speech he said he was excited to represent the district.
"I have been really humbled but at the same time feel really energised about what lies ahead. I look forward to giving the people of Clutha-Southland a strong voice in parliament regardless of who they voted for.
He said, given the size of the electorate, there are very different issues facing various parts.
It is such a big electorate, it is the size of Switzerland and there is all sorts of things happening. In Queenstown you are trying to manage growth and in the rest of the electorate you are trying to stimulate growth. But I look forward to working hard."
Mr Walker said he'd driven about 10,000km during the election campaign - something he promises to continue as the district's representative.