If you need a visa to visit Canada, then you will need a transit visa to travel through Canada without stopping or visiting. This is true even if you are in Canada for less than 48 hours. There is no fee for a transit visa. You can apply for a transit visa by filling out the application for a visitor visa (Temporary Resident Visa) and selecting transit visa from the list of options on the form.
If you need an eTA to visit Canada as of March 15, 2016, then you will also need an eTA to transit through Canada.
What is a Transit Visa?
A Transit Visa is a type of Temporary Resident Visa (TRV) required by anyone from a non-visa-exempt country who is traveling through Canada to another country and whose flight will stop in Canada for less than 48 hours. There is no cost for a transit visa, but the application process is the same as that for the TRV.
How to Apply for a Transit Visa
The Temporary Resident Visa (TRV) has three types: single entry, multiple entry, and transit. To apply for any one of these types of TRV, fill out the two-page application for a Temporary Resident Visa Made Outside of Canada or call the nearest Canada Visa Office. At the top of the application, you will choose the box named "Transit." Gather the necessary documents and mail in or take the application to a Canada Visa Office. You will not have to include a payment as the Transit Visa is free.
When to Apply for a Transit Visa for Canada?
Apply for a transit visa for Canada at least 30 days in advance of your departure or allow eight weeks if mailing it in.
Good to Know about Applying for a Transit Visa for Canada
Visitors must apply for a transit visa for Canada from their country of residence. You may not apply for a visa upon your arrival in Canada. Unless told otherwise, travel agents or cruise lines will not take care of your transit visa - it is your responsibility. Best Advice: call a Canada Visa Office in your country or your tour operator with any questions long before your departure.