The sale price for "La plage américaine" is far above the pre-auction estimate, which suggested the winning bid would be in the $500,000 to $700,000 range.
Lemieux, who died in 1990, is considered one of the foremost Quebec painters of the 20th century.
Another of his paintings, "Le mois de juin," sold for $380,250 at Thursday night's auction.
Other works up for sale Thursday night included Emily Carr's "Eagle Totem" and Lawren Harris's sketch "Lake Superior."
The auction was expected to bring in between $9 million and $12 million.