The upright piano is one of two from the film in which actor and singer Dooley Wilson sang "As Time Goes By," the signature song for lovers played by Humphrey Bogart and Ingrid Bergman.
The instrument from the Casablanca cafe owned by Bogart's character Rick is expected to sell for seven figures when it goes under the hammer as part of the sale by Bonhams and Turner Classic Movies (TCM) on Nov. 24 in New York.
The piano that was shown in flashback scenes in Paris in the film fetched $602,500 when it was sold at auction in 2012.
"We have some great pieces from Casablanca," said Catherine Williamson, the director of entertainment memorabilia at Bonhams.
All of the 30 "Casablanca" items in the sale are from a private collector. In addition to the piano, the auction will include interior and exterior doors from the Casablanca nightclub where Bogart and Bergman meet again and rekindle their romance.
Signed photographs by the film's cast members, the final draft of the original screenplay and passports and papers created for the movie will also be sold.
The auction will also include a gown worn by actress Rita Hayworth in 1946's "Gilda" and Barbra Streisand costumes from the films "On a Clear Day You Can See Forever," "The Way We Were" and "Yentl."
(Reporting by Patricia Reaney; Editing by Diane Craft)