Vast numbers of column-inches in the Canadian press were given over at the end of last week to news that Alsop had apparently won the scheme.
But at a press conference on Friday gallery chiefs announced that they had appointed former Frank Gehry employee Randall Stout (project pictured) as the surprise winner.
It is as yet unclear why so many observers had mistakenly tipped Alsop as the competition winner.
But Stout said he was delighted to have seen off the other shortlisted firms, which also included Zaha Hadid.
'It is an honour to be chosen from among such distinguished colleagues,' he said. 'I look forward with great excitement to crafting architecture that serves the Gallery's vision for the people of Edmonton and all of Alberta.'