An RCMP release says Ian Mcfadden, 35, and his nine-year-old son, James, entered the United States via the Blaine Border Crossing around 1:40 a.m. Saturday.
Once in Seattle they hired a taxi. They have not been seen since.
The McFaddens are from the West Shore area, located near Victoria.
Police say based on information received from people familiar with the pair, they have concerns for the well-being of the child.
Ian McFadden is 5-foot-8 and weighs 150 pounds. He has short brown hair and brown eyes. He was wearing a light brown single-breasted suit and a black fedora when last seen.
James McFadden also has brown hair and brown eyes. He was wearing khaki shorts, a black sweatshirt, and possibly a black-and- white hat.
Police say Ian McFadden has legal custody of his son. They are not aware of any crimes that may be related to this case.
"Out of an abundance of caution, we want to connect with Ian and James, and ensure that they are safe", said Cpl. Darren Lagan with the Vancouver Island RCMP.
"We are asking our neighbours to the south to assist us in locating Ian and James, and ask that they pass along any information they may have, to their local police."