Ardamullivan Castle was built in the 16th century by the Uí Sheachnasaigh (O'Shaughnessy) clan, rulers of the region known as Cenél Áeda na hEchtge until being disposed by Cromwell's invasion (1650s). It is first mentioned after the 1567 death of Ruaidhrí Gilla Dubh Ó Seachnasaigh. In 1579, Diarmaid Riabach Ó Seachnasaigh and his nephew John, fought each other in a dispute over the castle, which resulted in death for both. Diarmaid Riabach had previously acquired notoriety after betraying Richard Creagh, the fugitive Catholic Archbishop of Armagh, to the authorities.