It's 1940 on the Greek isle of Cephallonia, a place that's been familiar with various forms of tragedies throughout time. The latest is WWII encroaching upon their land. Local physician Dr. Iannis (JOHN HURT) and his young adult daughter, Pelagia (PENELOPE CRUZ), have no love loss for the Italians or Germans, with Pelagia recently becoming engaged to Mandras (CHRISTIAN BALE), a local young man who's now headed off to fight in the war.
As the months pass, however, Pelagia worries about her fiancée since she hasn't heard anything about or from him and soon believes the worst has happened. Things get worse, though, when an Italian artillery regiment arrives to occupy their land and one of its officers, Captain Antonio Corelli (NICOLAS CAGE), is assigned to stay in the their home. The hatred for the Italians is so great that the local government won't surrender to them, but instead do so to German Capt. Gunter Weber (DAVID MORRISSEY), and Pelagia wants nothing to do with Corelli.
The captain, however, is more of a musician than fighter, often leading his regiment - that's from his hometown and is yet to see any action - in song, with him leading the way on his ever present mandolin. His carefree and jovial ways soon begin to warm Pelagia's icy demeanor toward him, even with Mandras returning home, albeit as something of a changed man.
As Corelli welcomes seasoned Italian soldier Carlo (PIERO MAGGIO) into his regiment and spends time discussing the war with Weber, he finds himself drawn to Pelagia. The feeling is soon mutual and the two become lovers. Unfortunately, the real war eventually rears its ugly head, forcing the two lovers into making difficult decisions about themselves and their future together.