A native of Aberystwyth, John attended Ysgol Penglais before studying law at the University of Wales, Cardiff. After graduating in 1986, he studied theology at the University of Nottingham, graduating in 1988, followed by a Diploma in Pastoral Studies at St John's College, Nottingham in 1989. He was ordained deacon in the Diocese of St David's and a priest in 1990. Until his election as Bishop of Bangor, all his ministry was in the Diocese of St David's. Initially he was curate for Cardigan, Y Ferwig and Mwnt from 1989 to 1991 and then in Aberystwyth from 1991 to 1992. He was a vicar in the Rectorial Benefice of Aberystwyth from 1992 to1999. From 1999 he was vicar of Henfynyw with Aberaeron and Llanddewi Aberarth, to which was added Llanbadarn Trefeglwys in 2005. In 2006 he was appointed vicar of Pencarreg and Llanycrwys and the Archdeacon of Cardigan.
John was elected Bishop of Bangor on 9 October 2008 and was consecrated in Llandaff Cathedral on 29 November 2008, along with the new Bishop of St David's, Wyn Evans. He was enthroned in Bangor Cathedral on 24 January 2009.
- "Nottingham alumnus is the new Bishop of Bangor". University of Nottingham Alumni Online. www.alumni.nottingham.ac.uk. 2008-10-10. Retrieved 2011-02-02. "Andrew John, 44, grew up in Aberystwyth and graduated in Law at the University of Wales, Cardiff, in 1986, Theology at Nottingham in 1988 followed by a Diploma in Pastoral Studies in 1989 at St John's College, Nottingham."
- "The Right Reverend A T G John". The Church in Wales. www.churchinwales.org.uk. 2008-11-29. Retrieved 2011-02-02.
- Morrell, Anna (2008-11-17). "New Bishop of Bangor elected". The Church in Wales (www.churchinwales.org.uk). Retrieved 2011-02-02. "spent all his ministry so far in the Diocese of St Davids"
- Morrell, Anna (2008-12-01). "New Welsh bishops consecrated together". The Church in Wales (www.churchinwales.org.uk). Retrieved 2011-02-02. "The Very Rev Wyn Evans, Dean of St Davids, will be consecrated as the 128th Bishop of St Davids while the Venerable Andrew John, Archdeacon of Cardigan, will be consecrated as the 81st Bishop of Bangor. Both were elected while serving in the Diocese of St Davids."
- "The Diocese of Bangor - Who's Who - The Bishop of Bangor". The Church in Wales. www.churchinwales.org.uk. Retrieved 2011-02-02. "The Rt Revd Andy John Consecrated Bishop at Llandaff Cathedral on 29th November 2008, enthroned as 81st Bishop of Bangor, at Bangor Cathedral on Saturday 24th January 2009."
|Church in Wales titles|
|Bishop of Bangor