After graduating, Joy Mammen joined the Australian Opera as principal soprano. Her studies continued in Germany with Frederick Husler and Yvonne Rodd-Marling, and during this time she joined Aechen Opera and appeared as a guest artist throughout Europe. She returned to Australia for the Sutherland Williamson season at the Australian Opera where she sang La Traviata, L’Elisir d’Amore, La Sonnambula, as well as Eugene Onegin and Faust. She remained in Australia for the Williamson Theatres as well as appearing on TV and the ABC. Following this, Mammen moved back to London, teaching singing at the Royal Academy of Music and singing in opera and concert in Europe, the USA and Australia.