The Queen arrived at Canada House on Trafalgar Square with Prince Philip on Thursday morning.
She toured the new facilities and was presented with a set of keys to the building — a similar set to the one presented to her grandfather, King George V, when he opened the building in 1925.
Canada has brought together offices that were housed previously in two buildings — Macdonald House and Canada House. Macdonald House was sold in 2013.
"She saw many pieces of Canadian art hanging inside," said CBC's Ellen Mauro. "And the new atrium of the building was dedicated to her, named the Queen Elizabeth Atrium."
As the Queen arrived, dozens of people across the street from Canada House cheered and waved Canadian flags, Mauro said.
Canada's High Commissioner Gordon Campbell, a former premier of British Columbia, said Canada House serves as the country's "front door" for people in the United Kingdom.
"I hope when Canadians come, it reflects a little bit of what they see in Canada, in their part of Canada in particular," Campbell told CBC News.
There are 291 pieces of Canadian art on display at Canada House. They include works by:- Emily Carr.
- Group of Seven member Arthur Lismer.
- Photographer Edward Burtynsky.
- Sculptors Gathie Falk and Joe Fafard.
Former Canadian foreign affairs minister John Baird was among those who attended the opening ceremony.
Campbell said later that Canada is reducing its operating costs for the high commission by almost 50 per cent.
"We're generating $3 million a year in revenue from a Crown tenant here in the United Kingdom we never had before, and we'll be sending about $300 million-plus home, so for me, that's a pretty good deal for Canadians."
Macdonald House was sold for $562 million, he said, which more than paid for the refurbishing at Canada House.
Correction : An earlier version of this story said incorrectly that Queen Elizabeth was presented with keys similar to those given to her father, King George V. In fact, King George V was her grandfather.(Feb 19, 2015 8:50 AM)