The new West Aberdeenshire and Kincardine MP has insisted he will “work hard to represent everybody” in the constituency.
Stuart Donaldson seized the former Liberal Democrat stronghold, which Sir Robert Smith had held for 18 years.
Mr Donaldson took the seat with more than 22,000 votes, while the Tory candidate Alexander Burnett polled 15,916 and Sir Robert polled 11,812.
The new MP said: “I’m in a privileged position and I’m so glad the people of West Aberdeenshire and Kincardine have decided to put their faith in me.
“Robert Smith in the last 18 years has done a fantastic amount of work for the constituency but as tonight showed Scotland has chosen the SNP.
“Throughout this campaign I’ve worked hard to knock on every door and I’ll work hard to represent everyone in this constituency.”
Conceding defeat, Sir Robert said the SNP surge showed change to the electoral system was needed
He said: “Clearly there has been a vote for the Yes campaign that has rallied round the SNP and No voters had several parties they could have supported so we need to see electoral reform so all voices can be represented in parliament and not just one.
“It’s been a great privilege to represent West Aberdeenshire and Kincardine and I’ve enjoyed every minute of it.
“But that’s democracy and it’s important that democracy is seen to be working.”
Tory candidate Alexander Burnett, of the influential Burnett of Leys family, said he was “disappointed” with the surprise second place finish which he said was down to a split in the Unionist vote.
He said: “We can hold our heads up high after a terrific campaign.
“The only reason the SNP have done so well is because the Liberals and Labour have done so badly, but Conservative voters can look forward to a new government now.”
In 2010 Sir Robert held on to his seat by a margin of more than 7,000 votes, a 38.4% share, with Tory candidate Alex Johnstone coming second with 30.3% and the SNP’s Dennis Robertson third on 15.7%.
This year a high turnout of 75.2 % boosted the Nationalist vote in the wake of last year’s referendum, when thousands of new voters registered.
Early postal votes showed “surprisingly few Liberal votes” with SNP sources confident of taking the hard-fought constituency.
Sir Robert Smith has held the seat for 18 years, with his two major opponents in the SNP and the Tories fighting their first election.
High profile figures including Conservative ministers Michael Gove and George Osbourne and former Lib Dem leader Nick Clegg visited the constituency during the campaign.
The seat is a largely affluent area which is driven by the oil industry, farming, fishing and tourism.