University College Cork As a student at University College Cork, Costello also became involved in
Gaelic games. On 8 March 2012, he came on as a 16th-minute substitute to win an All-Ireland Freshers Championship medal following a 0-24 to 3-11 defeat of the
University of Limerick in the final.
Kilmallock Costllo joined the
Kilmallock club at a young age and played in all grades at juvenile and underage levels, enjoying championship success in the minor and under-21 grades before eventually joining the club's senior team. On 7 October 2012, Costello was named on the bench when Kilmallock faced
Adare in the
Limerick Senior Championship final. He remained on the bench for the entire game but collected a
winners' medal following the -15 to 0-15 victory. On 19 October 2014, Costello won his first championship medal on the field of play following a 1-15 to 0-14 defeat of reigning champions
Na Piarsaigh in the
final. He later won a
Munster Championship medal on 23 November 2014 following a 1-32 to 3-18 extra-time defeat of
Cratloe. On 17 March 2015, Costello was at left corner-back when Kilmallock suffered a 1-18 to 1-06 defeat by
Ballyhale Shamrocks in the
All-Ireland final at
Croke Park.
Limerick Senior On 14 December 2018, Costello was included on
John Kiely's first Limerick squad for the 2019 season. He made his first appearance for the team on 20 December 2018 when he came on as a 48th-minute substitute for
Lorcan Lyons in Limerick's 4-14 to 0-11 defeat of
Kerry in the
Munster League. On 9 March 2019, Costello made his first appearance in the
National League when he came on as a half-time substitute for
Tom Condon in the 2-22 to 0-11 defeat
Laois. On 31 March 2019, he was a member of the extended panel when Limerick defeated
Waterford by 1-24 to 0-10 to win the
National League title. On 30 June 2019, Costello won a
Munster Championship medal as a non-playing substitute following Limerick's 2-26 to 2-14 defeat of
Tipperary in the
final. ==Career statistics==