Playing senior rugby throughout the 1990s until his retirement in 2005, Costello's rugby career with
Leinster and
Ireland straddled the amateur and professional eras. He was part of the Irish team at the 2003 Rugby World Cup and also had spells with
Connacht and
London Irish.
Irish Rugby player file • Official Leinster caps: 126 • Points scored: 80 (16 tries) • Celtic League/Cup caps: 38 (5 tries) • Heineken Cup caps: 57 (5 tries) • Senior debut: Friendly, 46–11 win v Natal XV at Anglesea Road, 25 October 1995 • Heineken Cup debut: 24–21 win v Milan in Italy, 1 November 1995 • Ireland caps: 39 (January 1996 – 2004) • Ireland points: 20 (4 tries) • Ireland "A" caps: 9 • Ireland Under-21 caps: 2 • Ireland Schools caps: 4 • Leinster Under-20/21 caps: 1 ==Other work and family==