The Battle of Philippi was the final battle in the Wars of the Second Triumvirate between the forces of Mark Antony and Octavian ( the Triumvirate ) against the forces of Julius Caesar 's assassins Brutus and Cassius in 42 BC , at Philippi in the Roman province of Macedonia . The Battle of Philippi was the final battle in the Wars of the Second Triumvirate between the forces of Mark Antony and Octavian ( the Second Triumvirate ) against the forces of Julius Caesar 's assassins Marcus Junius Brutus and Gaius Cassius Longinus in 42 BC , at Philippi in Macedonia .