But two largely Sunni Muslim provinces had voted against, although one was by less than a key two-thirds majority, commission spokesman Farid Ayyar said on Monday.
The charter, which aims to lay a foundation for Iraq as it moves beyond the ousted government of Saddam Hussein, requires a simple majority to pass but will nevertheless be rejected if two-thirds of voters in three or more governorates vote against.
The majority Shia Muslim provinces of Basra, Dhi Qar, Karbala, Misan, Najaf and Wasit all voted massively in favour of the charter, Ayyar said.
By contrast, two Sunni Muslim-dominated provinces rejected the text, by 80% in Salaheddin and by 54% in Diyala, so the results from four other Sunni-dominated provinces in western and northern Iraq are crucial.
The tally from volatile western al-Anbar and northern Nineveh, which includes the mixed city of Mosul, were not yet known, Ayyar said.