Sernas was the son of Jokūbas Šernas, a signatory of the Act of Independence of Lithuania, who died when Jacques was a year old. His mother took him to Paris where he received his formal education. He joined the French Resistance and was captured and interned at Buchenwald.

His most recent appearances have been as a Cardinal in a TV film biopic of Pope John XXIII, Papa Giovanni (2002) and in Regina dei fiori (2005).

His most recent appearances have been as a Cardinal in a TV film biopic of Pope John XXIII, Papa Giovanni (2002) and in Regina dei fiori (2005).