[citation needed] On 7 October 2012, Costello was named on the bench when Kilmallock faced Adare in the Limerick Senior Championship final.
[2] 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.
[4] 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.
[7] 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.
[9] 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.