Following the announcement of Ger Cunningham's retirement from inter-county hurling on 14 January 1999, Cusack was promoted to Cork's first-choice goalkeeper. He lined out in all six of Cork's National League games that season before making his championship debut on 13 June in a 0–24 to 1–15 defeat of Waterford. On 4 July, he won a Munster Championship medal after a 1–15 to 0–14 defeat of reigning champions Clare in the final. On 11 September, Cusack was in goal for the All-Ireland final against Kilkenny. He kept a clean sheet and claimed a winners' medal following the 0–13 to 0–12 victory. Cusack was later honoured with his first All-Star award.