"Canada is always looking for ways to create hope and opportunity for our middle class as well as for people around the world," Finance Minister Bill Morneau said in a statement issued in Beijing.
"Membership in the AIIB is an opportunity to do just that."
The Beijing-based lender has been viewed by some as a rival to the World Bank and the Philippines-based Asian Development Bank, which was founded in 1966.
Critics worried that it would set much lower standards for projects and undermine principles of social, environmental and economic sustainability adhered to by the World Bank and other multilateral development finance institutions.
AIIB president Jin Liqun welcomed Canada's decision, which he said "shows its confidence in the strong foundations the bank has built in our first few months".
The United States, and Japan -- the world's largest and third-largest economies, respectively -- have notably declined to join the bank.
The announcement came during Prime Minister Justin Trudeau's visit to China, where he met Prime Minister Li Keqiang to try to strengthen ties before the G20 summit this weekend in Hangzhou.
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