Born Katina Constantopoulos in Pireas. Trained as an opera singer but changed career and joined the Greek Royal Theater in 1929. Paxinou distinguished herself on the stage. When World War II broke out she was performing in London and unable to return to Greece she emigrated to the US. She was selected to play Pilar in the 1943 film of For Whom the Bell Tolls, winning a Academy Award for Best Supporting Actress and a Golden Globe. She continued appearing in Hollywood films until 1949. Returning to Greece in 1950, Paxinou resumed her stage career. She formed the Royal Theater of Athens with Alexis Minotis, her principal director and her husband since 1940. She contiued to accept occasional film roles until her death in Athens in 1973.
For Whom the Bell Tolls (1943), Hostages (1943), The Confidential Agent (1945), Mourning Becomes Electra (1947), Uncle Silas (1947), Prince of Foxes (1949), Mr. Arkadin (1955), Rocco e i Suoi Fratelli (1960), Tante Zita (1968), Un Été Sauvage (1970).