The 1790 painting, by Johann Georg Edinger, is probably the last portrait made of the composer, who died in 1791 at the age of 35. The gallery plans to display the painting starting on Mozart's birthday, January 27.
The Gemaeldegalerie bought the painting in 1934 from a Munich art dealer. After a recent restoration, officials at the gallery showed it to Mozart expert Wolfgang Seiller, who concluded that it was of Mozart. A computer analysis found similarities between the painting and a painting of Mozart from 13 years before.
Mozart is believed to have sat for the portrait during his last visit to Munich.