I am a Vietnamese passport holder. I'm going back to Viet Nam from Montreal this December, and I will transit at Incheon Airport for a few hours. Do I need a Korean visa just for transiting, either from Montreal to Hanoi or from Hanoi back to Montreal?
No if you remain at the airport, have at least 6 months of validity on passport and have proofs on onward flight. Source: http://www.vinavisas.com/south%20korea-visa/vnm-vietnamese-passport/transit
You may not require a visa since Korea has an exception for holders of a Canadian visa.
Also, if you will remain airside, and any baggage is checked through to your final destination, then no visa will be required.
Korea (Rep.) (KR)
- Holders of a visa issued by Australia, Canada, Japan, New Zealand or USA to nationals of any country except for Cuba,