The instrument was used by actor Dooley Wilson in the 1942 movie as he performed on the famous song 'As Time Goes By'.
The piano went under the hammer at Sotheby's in New York for USD 600,000. The "Titanic" star was a part of the duo which made the private winning bid, reported New York Daily News.
DiCaprio and businessman friend Stewart Rahr are now planning to donate the piano to the Los Angeles County Museum of Art.
Experts had predicted the studio piece would fetch as much as USD 1.2 million at Friday's sale.