Financial terms of the deal were not disclosed.
Porter president and chief executive Robert Deluce says the deal will help the company strengthen its core business and help position it for growth.
"Nieuport Aviation is a seasoned airport operator that will deliver exceptional service at the terminal and help build on the existing overall superior travel experience for passengers," Deluce said in a statement.
Billy Bishop is the main base for Porter Airlines, which started flying in October 2006.
Through its City Centre Terminal Corp. subsidiary, Porter has spent millions upgrading and expanding the terminal that saw more than two million passengers last year.
Nieuport Aviation includes InstarAGF Asset Management Inc., Kilmer Van Nostrand Co. Ltd., Partners Group and institutional investors advised by J.P. Morgan Asset Management.
"The terminal is a premier essential transportation infrastructure asset with an established operating history, robust contractual framework and positive long-term outlook," InstarAGF president and chief executive Gregory Smith said in a statement.
Billy Bishop is a popular choice for business travellers because of its easy access to downtown Toronto.
The sale comes as Porter seeks to expand its operations at Billy Bishop in a controversial plan that would see it start flying jets from the airport located on Toronto's waterfront.
The plan requires extending the airport's runway at both ends by filling in part of Lake Ontario.
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