The Hong Kong Government has advocated teaching Cantonese opera in the school music curriculum to promote Chinese culture education. This longitudinal study aims to examine how and why teachers transform within 3 years in learning and teaching Cantonese opera with a teacher-artist partnership approach in schools. Five primary and two secondary teachers collaborated with a Cantonese opera artist to teach the genre for 8 weeks in 2008. With reference to the Transformative Learning Theory, two rounds of interviews with teachers in 2008 and 2011 were carried out to investigate the extent they had transformed in relation to teaching Cantonese opera. Informational learning from the partnership and self reflection in sufficient time are the main attributes in teachers' transformation. It is implied that music teachers may reinterpret their old experience of learning the Chinese music with the assistance of relevant experts in order to make new meaning of their perception on music education.