[citation needed] His father Seán Ó Ceallaigh was elected a Fianna Fail TD for County Clare in a by-election 1959.

[citation needed] As an Auxiliary Bishop, he assisted Archbishops of Dublin Desmond Connell and Diarmuid Martin in the governance of the diocese.

Pope Benedict XVI accepted his letter of resignation on 17 September 2009 but did not name another auxiliary bishop to replace Ó Ceallaigh.

[citation needed] Upon his resignation being accepted Archbishop Martin said: "Bishop Fiachra’s warmth and particular personal qualities enriched our work.

He said Bishop Ó Ceallaigh, "particularly as he struggled with illness in recent years, was an outstanding witness to the motto he took on his episcopal appointment, Dia Ár Misneach (God is our courage)".