He played Irish leader Michael Collins in The Treaty (1991) (TV). He later had a supporting role in the biopic Michael Collins (1996).

He has four sons from his marriage to Mary: Domhnall, Fergus, Brian and Rory.

Participated in the Dublin Shakespeare Theatre Festival the during mid-eighties.

He was a teacher for 10 years before becoming an actor

He has starred in feature films with two of his sons: Studs (2006) with his eldest son Domhnall Gleeson, and The Tiger's Tail (2006) with his second youngest, Briain Gleeson.

Joined the Royal Shakespeare Company (RSC) in Stratford Upon Avon, England, in the late eighties for two seasons where his credits included King Lear and King Richard II.

He started acting at the age of 34.

He taught English, Irish & Physical Education at Belcamp College Secondary School in Dublin.

Attended the Royal Academy of Dramatic Art in London, England.

Associate Member of RADA.

Plays a professor of Defense Against the Dark Arts in Harry Potter and the Goblet of Fire (2005), Harry Potter and the Order of the Phoenix (2007), and presumably any subsequent films in which his character, Mad-Eye Moody, appears. This makes him the first, and to date, only actor to play a Hogwarts professor who has himself been employed as a teacher.

Frequently plays wise, experienced men who act as mentors and father figures to the lead characters.

Taught Maths at St. Joseph's Secondary school in Fairview, Dublin.

He is a fine fiddle player and can be seen playing it in Michael Collins (1996) and also in Cold Mountain (2003).