Her 16,256 election night votes gave her a huge 6922 vote margin over Labour's Lesley Soper, who gained 9334 votes.
Her margin surpassed that of retiring Invercargill MP Eric Roy, who headed off Ms Soper by 6263 votes in 2011.
A beaming Ms Dowie (40), a solicitor and mother of two preschoolers, said she "would have been happy with a one vote win'', but it was "fantastic'' she had topped Mr Roy's margin.
She said she wanted to "hit the ground running'' in Parliament so she could "get wins on the board''.
Invercargill was a Labour stronghold for four terms between 1993 and 2002 and Ms Soper, who was an MP for short periods in 2005 and 2007-08, had high hopes of winning it back against the National newcomer.
But it was not to be, and Ms Soper's personal support dropped from 11,012 election night votes in 2011 to 9334 this time.
She said this would be her last political campaign on the national stage.
"I believe I had a great deal to offer, but the people of Invercargill have made their choice. I'll still be Labour, of course, but it is time to refocus my life.''
