Purpose - This study investigated the effectiveness of a professional development project on digital citizenship education (DCE) conducted by a team at the Education University of Hong Kong. The project aimed to promote digital citizenship education in local junior secondary schools in Hong Kong and support the professional development of in-service teachers.Design/methodology/approach - This study was based on a departmental knowledge transfer and curriculum development project that provided professional development training workshops to in-service teachers from seven partner schools. This paper analyses some findings from the quantitative research questionnaires, lesson observations and qualitative interviews.Findings - Eleven of the 12 participants reported that they were satisfied with the training workshops in the end. We also conducted paired sample t-tests of inferential data. The results show that after the workshops, the teachers tended to teach their students more about aspects of digital law, digital commerce and digital safety and security when teaching digital citizenship. This selection helps us to better understand the priorities of teachers in teaching digital citizenship.Originality/value - This paper is the product of an original knowledge transfer and curriculum development project supported by the Education University of Hong Kong in the Hong Kong Special Administrative Region (Hong Kong SAR) of China. The topic of digital citizenship education has also been under developed since citizenship education has always been about conventional citizenship in the physical world. Copyright © 2021 Emerald Publishing Limited.