This qualitative study has investigated how a group of bilingual university students in Hong Kong understand digital citizenship and construct it through digital literacy practices in social media. Drawing on interview data and examples of digital activity shared by the students, we adopt the theories of digital literacies and translanguaging and transsemiotizing to reveal how they construct digital citizenship through an complex interplay between several factors, most prominently (1) a variety of digitally mediated social, cultural and educational practices the students engage in, (2) their agency of deploying diverse linguistic and semiotic recourses to achieve varied communicative effects in different settings and (3) their personal pursuits of intellectual and professional development and social engagement in a digitalized and globalized society. We then discuss how the findings can enrich our understanding of digital citizenship and its relationship with digital literacies in a multilingual and multicultural context such as Hong Kong. The implications for digital citizenship education are also discussed. Copyright © 2023 The Authors. Published by Elsevier Inc.