Instead, O'Leary said he will endorse candidate Maxime Bernier because, due to lack of support in Quebec, he wouldn't win the general election after all, according to an interview with Toronto-based The Globe and Mail.
"It's for the sake of the party that I do this, and the country," O'Leary said in an interview with The Globe and Mail at his downtown Toronto office. "Because I can't deliver Quebec."
O'Leary first announced in January that he planned to make Canadian Prime Minister Justin Trudeau's life "absolute hell" by joining the race for Conservative leadership.
O'Leary, a native Canadian, said what inspired him to get politically involved was tied to Trudeau's policy choices and his aversion to newly inaugurated U.S. President .
"All [Trudeau's] policies on corporate tax, carbon tax, tax this, tax that, are completely out of sync with the U.S.," O'Leary told CNBC at the time. "He should have used the Trump election to basically pivot. He didn't do that."
O'Leary told The Globe and Mail on Wednesday that the only reason he is endorsing Bernier now is because he believes Bernier can win in the province, and O'Leary's follower base should follow his decision, he added.
Elections for Canada's Conservative Party leadership are scheduled to take place on May 27. The country's next general elections are scheduled for Oct. 21, 2019.
Disclosure: CNBC owns the exclusive off-network cable rights to "Shark Tank."