Suncor Energy said an announcement for Brian Demosky's replacement would be made in due course.
Demosky takes over from Brian Grassby as Canadian Pacific's CFO, the company said.
Billionaire investor William Ackman won a proxy fight and installed a new chief executive at Canadian Pacific last year.
The company, Canada's second-largest railway, said in October that Ackman had sold 6 million company shares, but his firm, Pershing Square, remains the biggest shareholder with a 10 percent stake.
Shares of Suncor Energy closed at C$36.52 while shares of Canadian Pacific closed at C$160.71 on Thursday on the Toronto Stock Exchange.
Reporting By Narottam Medhora; Editing by Joyjeet Das