Updated Sept 2013
Bottom Line: U.S. and Canadian citizens ages 15 or younger with parental consent will be allowed to cross the borders at land and sea entry points with certified copies of their birth certificates rather than passports.
Visitors of all ages arriving in Canada by air require a passport or passport equivalent.
If you need a passport right away, get a passport within 24 hrs with Rushmypassport.com
U.S. and Canadian citizens ages 16 through 18 traveling between the U.S. and Canada with school, religious, cultural or athletic groups and under adult supervision will also be allowed to travel with only proof of citizenship, such as a birth certificate.
Children may require additional travel documents when visiting Canada. See Tips for Crossing the Border with Children for more info.
Visitors of all other nationalities, of all ages, need a valid passport to enter Canada by land, sea and air.
Best Advice: Don't wait. Get a passport or passport equivalent, like a NEXUS Card, for your child now. The trend for essential travel documents, even between neighbouring countries like Canada and the U.S. and Mexico, is toward increased security and standardization. A passport - or passport equivalent - is becoming a must.