At inter-county level, Cusack was part of the successful Cork minor team that won the All-Ireland Championship in 1995 before later winning back-to-back All-Ireland Championships with the under-21 team in 1997 and 1998. He also won an All-Ireland Championships with the intermediate team in 1998. He joined the Cork senior team in 1996. Cusack eventually succeeded Ger Cunningham as first-choice goalkeeper and made a combined total of 137 National League and Championship appearances in a career that ended with his last game in 2012. During that time he was part of three All-Ireland Championship-winning teams – in 1999, 2004 and 2005. Cusack also secured five Munster Championship medals and a National Hurling League medal. He announced his retirement from inter-county hurling on 6 March 2013.