The vote delivered a victory for Prime Minister Mark Carney and supporters of Canadian unity amid US President Donald Trump's trade war and annexation threats.
The province's first-ever vote on separation was not a direct referendum on independence but would have set Alberta on a path towards a future vote on splitting from Canada.
With more than one million votes counted early on Tuesday, about 76 per cent supported remaining in Canada, compared with 23 per cent who backed beginning a process that could lead to separation.
Carney earlier urged Albertans to deliver a decisive vote for unity.
"Vote like Canada's future depends on it because it does," he told a rally Friday in Edmonton, where he grew up.
Alberta, home to the world's fourth-largest proven oil reserves, is cowboy country and a conservative stronghold whose political culture has long had more in common with the American West than much of Canada.
Resentment towards Ottawa runs deep, but has not traditionally translated into widespread support for independence.
Trump's trade war and threats to make Canada the 51st US state have helped Carney rally support in Alberta, where Liberal prime ministers have historically been unpopular.
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