Canada will contribute the equivalent of £19.7m to a British-led partnership buying air defences for Ukraine.
The UK, US, Netherlands, Denmark, and Canada aim to purchase hundreds of short and medium-range missiles and systems.
Canada’s donation forms part of a £298m military aid package announced by Prime Minister Justin Trudeau in June.
The country, home to one of the world’s largest Ukrainian diasporas, has been a vocal supporter of Kyiv.
Since the war began Canada has committed £5bn in aid.