28 years of age, Costello was born in Dingle, Co Kerry and has lived in Limerick for the past 24 years. He went to school in Ard Scoil Ris and on then to the University of Limerick, where he completed a Sport and Exercise degree, graduating in 1999.

He has recently completed a Certified Strength and Conditioning course with the NSCA of America and a Sales and Marketing business diploma.

He began playing rugby as an eight year-old with Garryowen FC and for the past seven seasons has played senior rugby with UL/Bohemians.

A Level 2 coaching coach, he has been involved coaching various teams in UL/Bohemians Ard Scoil Ris and University of Limerick.

Having managed a Sports Centre in Tipperary - he was also employed as a part-time fitness advisor with the IRFU - he established his own Fitness Consultancy Company in March 2004, which he managed until beginning his current employment with Munster Rugby.