"Over time the government has lost its way," said Prentice, who will soon be sworn in as Alberta's 16th premier.
"Watching from afar, I was as disappointed and frustrated as anyone.
"I wasn't at the table when those decisions were made, but I'm at the table now," he said to applause from about 350 party supporters.
"I can tell you this: I will restore a commitment to fiscal prudence and ethical conduct in Alberta."
The 58-year-old former Calgary Conservative MP and cabinet minister handily defeated former provincial cabinet ministers Ric McIver and Thomas Lukaszuk in a vote overshadowed by computer and phone foul-ups that left some members saying they were unable to cast a ballot.
Prentice takes over a PC government that has fallen sharply in the polls this year following the travel and spending controversies of former premier Alison Redford.
Prentice captured almost 77 per cent of the 23,386 votes cast, well over the 50 per cent plus one needed to avoid a run-off vote.
McIver, the member of the legislature for Calgary-Hays, took 12 per cent.
Lukaszuk, the member for Edmonton-Castle Downs, collected 11 per cent.
McIver ran a campaign based on fiscal austerity and debt paydown. He told reporters he respects the results and will work with Prentice and the PC caucus.
"I was able to put forward ideas I believe in," said McIver. "I feel we made a difference and impacted the future direction that our party and our government will go."
Lukaszuk did not speak to the media after the results were announced but later tweeted: "I did my best under the circumstances. I will continue to serve Albertans any way I can."
Prentice now needs to gain a seat in the legislature. He has already promised to call a byelection as soon as possible.
The only vacant seat is the one that was held by Redford, although Neil Brown of Calgary-Mackay-Nose Hill has previously offered to leave his seat so Prentice can run.
Speaking to reporters, Prentice wouldn't give specifics on his byelection plans.
The next general election is slated for the spring of 2016.
His main opponent will be the Wildorse party, which surged ahead of the Tories as the scandals unfolded.
In a news release, Wildrose Leader Danielle Smith congratulated Prentice, but said he "has a tremendous road ahead of him in order to rebuild trust with Albertans and get a grip on a government that has spiralled out of control."
NDP member Deron Bilous said he didn't think much of Prentice's promise to reinvigorate the PCs, saying Redford, too, had promised renewal.
"All were doing is throwing a new coat of paint on an old beater," said Bilous.
Liberal Leader Raj Sherman, in a news release, agreed: "What Alberta really needs is a change in government."
Redford resigned as premier in March with a caucus revolt brewing over her leadership style and spending.
She resigned her seat last month ahead of a damning auditor's report examining her travel expenses that was forwarded by the government to the RCMP.
Prentice had been the favourite from the time he announced his candidacy.
Almost all members of the PC caucus announced their support for him. His campaign raised $1.8 million, more than double the $300,000 raised by Lukaszuk and $417,000 raised by McIver combined.
His pedigree is in federal politics. He served as minister of environment, aboriginal affairs and industry while in Prime Minister Stephen Harper's government.
Harper congratulated Prentice after the results were announced.
"I look forward to working with Mr. Prentice on issues of importance for Albertans and all Canadians, including the economy, responsible resource development and job creation," Harper said in a news release.
Prentice quit federal politics in 2010 to take an executive position with CIBC.
During the campaign, he pledged to not hike taxes or tinker with oil royalties. There will be an accelerated paydown of Alberta's debt and a push to get new schools built.
Prentice has also promised a slimmed-down cabinet to reflect his government's commitment to fiscal austerity.
While he promised integrity, Prentice was pilloried by Lukaszuk and McIver during the campaign for giving away memberships to supporters. The party had asked all candidates to sell the memberships at $10 apiece. Lukaszuk and McIver labelled the actions underhanded and undemocratic.
It was the party's third leadership vote in eight years, and the number of voters continued to decline.
In 2006, 97,000 voted in the first ballot in the campaign ultimately won by Ed Stelmach. In 2011, 59,000 voted on the first ballot in a race Redford eventually won.
This was the first time the PCs gave voters the option of voting online or by phone as well as casting a ballot in person.
It was a rocky process. Over Friday and Saturday, voters complained that they had not received the required 20-digit PIN. Others had a PIN but were disqualified due to home address mix-ups or for other reasons.
Still others reported facing long delays or not being able to gain access to the system at all.
Party executive director Kelley Charlebois acknowledged "there were problems," but said the final result reflected the membership sales.
He said he expects party rank and file will debate the e-voting process at the annual meeting in November.