Hancock, Premier Alison Redford's second in command, was chosen by the governing Progressive Conservative caucus to replace her when she steps down on Sunday and her party begins the search for a permanent replacement.
Hancock, deputy premier and member of the legislature for Edmonton-Whitemud, has been in government for 17 years and is the longest-serving minister in cabinet.
He lost the PC leadership race to Ed Stelmach in 2006 and said Thursday he won't run again because the Tories need a fresh face.
"If we're going to show the party as moving forward, I'm probably not the guy who epitomizes that," he said.
The PC party executive is to meet Monday to set out the timeline for the leadership race, which can run as little as four months and as long as six.
Redford did not attend the hour-long morning meeting to choose Hancock, but arrived at the end with her 12-year-old daughter, Sarah, in tow. She did not speak to reporters.
Hancock said he will neither be changing Redford's policies nor the direction of government. That's the prerogative of the incoming permanent leader, he suggested.
"The mandate doesn't change," said Hancock.
"It's the mandate of government. It's the mandate under which our MLAs were elected and that is what we will continue to do."
Hancock said he will also keep his portfolio as advanced education minister.
Thursday was Redford's last day to sit in the house as premier for question period, but she did not appear.
Government house leader Robin Campbell used her desk for his paper overflow.
The three opposition leaders offered short tributes to her empty chair, thanking Redford for her service to the province.
After each tribute, Redford's caucus members half-heartedly thumped their desks in support, though some didn't even do that.
Their biggest and loudest cheer came when Hancock was recognized in the house as the new leader.
Hancock had been Redford's most vocal supporter in recent weeks as mounting revelations of lavish spending and caucus turmoil swamped her ability to govern.
Redford quit Wednesday night, saying the infighting had become an intolerable distraction to the business of the province. She left just hours before PC riding association leaders were expected to unite in a bid to demand she quit.
Redford remains the member of the legislature for Calgary-Elbow.
Hancock said that despite the race, the business of government will carry on and will be effective.
"We've got a budget to pass and we're going to pass that budget," he said. "We are going to go into the legislature every day and do our job, and we are going to go back into our constituencies every day and do our job," he said.
"We're all professionals. We all know our jobs. We all know what the people of Alberta elected us to do. We come to work every day."
When asked if he expects difficult times ahead, Hancock replied: "In this business, every day is a difficult day."
Speculation is growing on who will run to become leader and take the part into the next election in the spring of 2016.
Service Minister Doug Griffiths, who lost to Redford in the last leadership race, said he isn't interested in running again. He has family considerations that need his attention, he said.
At least a couple of other ministers were hedging their bets.
Finance Minister Doug Horner said it was too early to say, but wasn't ruling out another run at the leadership. Horner was one of the top contenders in the race that Redford won in the fall of 2011.
"I've made no decisions about my future at this point," Horner said. "Yesterday was a bit of a shock for a lot of people and we are going to take stock and make some decisions in the future about my future."
Employment Minister Thomas Lukaszuk, while also saying it was still early going, wasn't discounting his own run.
He dismissed suggestions from the opposition that the party's leadership race — the third in eight years — will distract from the business of government. "We can walk and chew gum at the same time," he said.
If opinion polls are any guide, the new leader will have work to do. The PCs dipped to historically low popularity levels under Redford.
Opposition Wildrose Leader Danielle Smith said leadership is not the issue. She said the problem is a PC party that has been in power too long and has forgotten what it means to serve the public.
"It doesn't really matter who the leader of this PC party is. They are still rudderless (and) directionless," said Smith.
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