The former federal cabinet minister and CIBC vice-chair tweeted Friday at 3:14 p.m. MT saying he is an official candidate in the race.
He also changed his Twitter profile description to include the phrase, "Running for @PC_Alberta leadership."
Since CBC News reported that Prentice will be running in the PC leadership race, several MLAs have publicly supported him.
Provincial Health Minister Fred Horne, Education Minister Jeff Johnson and acting Municipal Affairs Minister Greg Weadick have given their support, as have Health Services Minister Manmeet S. Bhullar and Associate Regional Recovery Minister Kyle Fawcett.
Alberta Justice Minister Jonathan Denis also endorsed Prentice on May 11.
So far, Prentice and provincial Transportation Minister Ric McIver are the only candidates to replace former premier Alison Redford.
Redford resigned in March over allegations of improper spending and party infighting.
As for Prentice, he left federal politics 3½ years ago after holding several key portfolios in Stephen Harper's government, including environment and aboriginal affairs.
Since then he's been vice-chairman of CIBC and, more recently, took on the role of helping Enbridge work with First Nations opposed to the company's proposed Northern Gateway pipeline through British Columbia.
He's also on the board of the Canadian Pacific Railway and has said he will remain a member while running for the PC leadership, but will resign the board position if he wins.