The oil-on-canvas piece, called "Gather Ye Rosebuds While Ye May," was painted by British artist John William Waterhouse in 1909 and depicts young women picking flowers in a meadow. The composition comes from the Robert Herrick poem of the same name.
The painting was obtained by the unidentified Canadian couple in the early 1970s when they bought an Ontario estate and its entire contents - including the artwork.
Sotheby's believes the painting wound up in the house after the previous home owners purchased it from a private Canadian collection.
The husband and wife who currently own the piece are now selling it in an effort to scale down their possessions as they prepare to retire.
Sotheby's vice-chairman Ben Doller says the painting has an unusual, arched top and is in superb condition.
It's expected to sell for between US$1.75 million and $2.5 million.
