[4] In 1603 the Treaty of Mellifont was agreed between the English Crown and Hugh O'Neill, Earl of Tyrone, in the abbey grounds.

[5] Mellifont was then the property of The 1st Viscount Moore, who was a close friend of Lord Tyrone, and helped persuade him to sign the Treaty.

Little of the original abbey remains, save a 13th-century lavabo (where the monks washed their hands before eating), some Romanesque arches and a 14th-century chapter house.

New Mellifont Abbey is home to the Cistercian monks and is located in Collon, a small village and townland in the southwest corner of County Louth, on the N2 national primary road.

[6] Supported by Cardinal McRory, it was re-established in 1938 by monks from Mount Melleray Abbey who purchased Oriel Temple, the residence of Lord Massareene (formerly the residence of First Baron Oriel John Foster MP the last Speaker of the Irish House of Commons), the land was originally owned by the old Mellifont Abbey.

In 1998 Dr. Sean Brady (future Cardinal) and Cardinal Cahal Daly officiated at a mass with the Mellifont community at the old Mellifont Abbey, to celebrate 900 years since the Cistercian order was established in Ireland, and the 850 anniversary of the death of St. Malachy, as well as the 60th anniversary of the re-establishment of the community.