Bishop Treanor was born on 25 December 1950 in Siverstream (Ireland). He studied
art and philosophy, then turned towards theology and completed his licentiate. On 13 June 1976 he was ordained a priest and on 29 June 2008 was consecrated a bishop, for the diocese of Down and Connor.
From 1993 to 2008 he was Secretary General of the Commission of the Bishops' Conferences of the European Community in Brussels. Bishop Treanor became a member of COMECE in 2009.