Southern Ontario backbench MP Ed Holder has also been brought into the cabinet fold, replacing Rickford as minister of state for science and technology.
In the past, even small cabinet shuffles have been documented with news releases and backgrounders. This time — and for the second time in less than a year — Harper relied instead on Twitter to announce his newest lieutenants.
"I just named Joe Oliver Canada's new finance minister," the prime minister tweeted as the new ministers were sworn in at Rideau Hall. "He will continue to strengthen the economy & balance the budget by 2015."
An hour later, he issued a five-paragraph statement on the shuffle.
"Mr. Oliver, Mr. Rickford and Mr. Holder bring with them a wealth of skills, knowledge and experience and I am confident that they will deliver results and provide strong leadership in these important portfolios," the statement said.
Oliver, 73, is widely respected within the Harper cabinet and Conservative party and is known on Bay Street, where he spent decades as an investment banker.
He went on to become executive director of the Ontario Securities Commission and then president of the Investment Dealers Association of Canada
His sometimes gruff and often partisan demeanour is much different from that of the jocular Flaherty, who often poked fun at himself.
The 46-year-old Rickford, who has served as MP for Kenora since 2008, retains responsibility for economic development in Northern Ontario, including the region's Ring of Fire mineral deposit.
He will also become the government's point man on the tricky Keystone XL pipeline project, which is still awaiting approval in the U.S.
Holder, 59, is an insurance broker from London, Ont., who was first elected to Parliament in 2008.
Flaherty was Harper government's first and only finance minister until his departure, which he unexpectedly announced late Tuesday.
He managed the economy through the crippling recession of 2008-2009. He went deep into the red with large deficits, but left the books virtually balanced after his Feb. 11 budget.
Flaherty said his decision was made with his family earlier this year. He said it was unrelated to a rare skin condition that requires him to take medication, which includes weight gain and apparent fatigue among its side effects.
"As I begin another chapter in my life, I leave feeling fulfilled with what we have accomplished as a government and a country during one of the most challenging economic periods in our country's history," Flaherty said in a statement.
He will continue to sit as the member of Parliament for the riding of Whitby-Oshawa.