Mr Hastie was ahead of Labor's Matt Keogh 55.7 to 44.3 per cent on a two-party preferred basis with 60 per cent of votes counted. The ABC was predicting a Hastie win a little over an hour into counting.

The result represents a 6.2 per cent swing from the government but Labor needed another 5.6 per cent to win.

Don Randall – whose sudden death sparked the byelection – held the seat with an 11.8 per cent margin.

It's believed the leadership turmoil in Canberra helped rather than hindered Mr Hastie, with support swinging back behind the Coalition in the wake of Tony Abbott's ouster.

Under Mr Abbott the Liberals feared a double digit swing.

Mr Turnbull did not travel to Canning to the campaign but described Mr Hastie as a "fantastic" and "phenomenal" candidate when he spoke to the media during a community meet and greet in Sydney.

But Mr Turnbull's deputy, Foreign Minister Julie Bishop, was at Mr Hastie's side when he made his victory speech.

"I predict that Andrew Hastie will have a long and successful career as a member of Parliament. He will make a mighty contribution to the public life of this country," Ms Bishop said.

Mr Hastie paid tribute to Mr Randall and his family.

"Politics itself is a new experience for me," he said. "I go to Canberra as someone with much to learn.

"I don't understand every political process or issue and I won't pretend to.

"But I'll be guided by the values that have been tested in the defence of our nation and that I believe are essential to effective leadership - honour, integrity, compassion, humility, and service."

"I'll make mistakes like any new member of Parliament, but I will always strive to do the right thing."

Conceding defeat, Mr Keogh said Labor had fought a "noble fight" and a 6 per cent swing was a "huge effort".

"The fire within me to fight for my local area, to fight for WA, to stand up in our national parliament on behalf of all of those people is greater now than it's ever been and I really wish to continue that fight into the future," he said.

Labor and the unions campaigned hard on the perceived risk to local jobs of the China-Australia free trade agreement.

A ReachTEL poll in The West Australian newspaper showed the strategy worked, with 52.5 per cent of voters worried about the deal.

But Labor's heavy emphasis on Mr Abbott ultimately backfired. Campaign staff are said to have spent dozens of hours removing references to Mr Abbott from campaign posters and placards in recent days.

On polling day, many Labor supporters were armed with new placards showing a black and white picture of Mr Abbott with Ms Bishop underneath the word "Loyalty".

Earlier, Ms Bishop brushed off the attack.

"This is not about me. This by-election is about Andrew Hastie versus the other candidates that have been put forward," she said.

Mr Hastie's campaign began with controversy about troops he commanded in Afghanistan cutting the hands off dead Taliban soldiers. He has been cleared of any wrongdoing.

He drew fire from Opposition Leader Bill Shorten last week for suggesting Labor didn't support troops in Afghanistan.